Police responses to intimate partner violence incidents involving children: Exploring variations in actions and concerns in an Australian jurisdiction

BACKGROUND

Intimate Partner Violence (IPV) has transformed from a private matter into a global concern. Although progress has been made in enhancing police responsiveness to IPV, research on interventions in IPV cases involving children remains limited.

OBJECTIVE

This study investigates how police officers' responses vary depending on the nature and severity of IPV incidents and explores disparities in their responses when children are present at IPV incidents.

PARTICIPANTS AND SETTING

175 police officers (126 males, 49 females) in a single Australian jurisdiction.

METHODS

A mixed-methods approach utilized an online survey with four hypothetical IPV scenarios to capture anticipated responses. The quantitative analysis assessed officers' recognition of incident seriousness and willingness to take action, while the qualitative thematic analysis explored reasons for response modifications in the presence of children.

RESULTS

The quantitative analysis revealed that officers consistently recognized the seriousness of IPV incidents and displayed a willingness to take various actions, such as initiating investigations and detaining perpetrators. Thematic analysis of qualitative data uncovered officers' reasons for modifying or maintaining their responses to IPV incidents with child presence. Concerns for child safety, emotional impact on children, and breaking the cycle of violence were identified as key drivers for officers' modified responses. Additionally, some officers adhered to standard procedures, emphasizing their legal obligations and the adequacy of their existing actions.

CONCLUSIONS

This study contributes to an enhanced understanding of the complex decision-making processes among police officers when responding to IPV incidents involving children, highlighting the necessity of balanced policies and comprehensive training to navigate these complexities effectively.

Salvage total glossectomy and total glosso-laryngectomy: Are they worth it? A GETTEC French multicenter study

BACKGROUND

Salvage total glossectomy (TG) or total glosso-laryngectomy (TGL) remain controversial, as highly morbid procedures. The objective was to describe oncological and functional outcomes after salvage TG or TGL.

METHODS

We performed a multicenter retrospective study, including patients with previous neck irradiation undergoing TG or TGL for squamous cell carcinoma involving the base of tongue.

RESULTS

We included 42 patients: 27 in the TG group and 15 in the TGL group. For the entire cohort, median OS and DFS were estimated at 19 months (95% IC [14-44]) and 10 months (95% IC [7-13]) respectively, with no difference between the two groups. After a median follow-up of 90 months, 10 patients (24%) were alive and free of disease. Att he end of follow-up, we noted a gastrostomy dependency of 89% and 87 %respectively in the TG and TGL group, and 48% of patients in the TG group had a tracheotomy.

CONCLUSION

Although local control is difficult to achieve after salvage TG or TGL, these procedures are associated with acceptable survival and chance of cure for a last-resort situation. TG and TGL can be proposed in selected motivated patients after careful shared decision-making.

Psychological Autopsy: A Method to Assist in the Identification of Risk and Protective Factors for Intimate Partner Femicide

The most common form of violence experienced by women is that perpetrated by intimate partners, and the gendered nature of intimate partner femicide (IPF) has received particular attention. Few studies to date have delved into the limitations associated with methods used in IPF research, and particularly the methods used to study homicide victims (rather than homicide perpetrators). This article outlines dominant methodologies used to study IPF, and considers a novel method of investigation-the "psychological autopsy"-that may help to improve existing knowledge about IPF.

Exploring Intimate Partner Violence Before, During, and After Pregnancy in Bangladesh

Intimate partner violence (IPV) against pregnant or postpartum women is known to have multiple detrimental effects on women and their children. Although results from past research suggest much continuity in trajectories of IPV, it is unclear whether pregnancy interrupts or augments these patterns. Little is known about how physical, sexual, and psychological IPV change and overlap throughout a woman's transition to parenthood. Relying on population-based data, this study examines the prevalence, co-occurring nature, and the changing patterns of physical, sexual, and psychological IPV before, during, and after pregnancy in Bangladesh. Cross-sectional survey data were collected between October 2015 and January 2016 in the Chandpur District of Bangladesh from 426 new mothers, aged 15 to 49 years, who were in the first 6 months postpartum. IPV was assessed with a validated set of survey items. The frequencies of different types of IPV victimization according to the period of occurrence were calculated separately and in a cumulative, co-occurring manner. The prevalence of physical IPV before, during, and after pregnancy was 52.8%, 35.2%, and 32.2%, respectively. The comparative figures for psychological IPV were 67.4%, 65%, and 60.8%, and for sexual IPV were 21.1%, 18.5%, and 15.5%, respectively. The results demonstrate a notable continuity in IPV victimization before, during, and after pregnancy. Psychological IPV is the only type to exhibit a significant reduction during and after pregnancy, compared with before pregnancy, but it commonly overlaps with physical IPV, which shows a significant change during pregnancy and little change in the postpartum period. At the same time, pregnancy and childbirth offer little protection against IPV for women in relationships characterized by psychological or sexual victimization, both of which commonly overlap with physical IPV. Results reinforce the need to conduct routine screening during pregnancy to identify women with a history of IPV and to offer necessary help and support.

Alcohol and drug problems among Australian homicide offenders

BACKGROUND AND AIMS

Most homicide studies focus upon 'acute' situational intoxication as opposed to 'chronic' substance misuse. The aims of the study were to: (1) determine the extent of homicide offenders' alcohol and drug use in the year preceding the homicide; (2) compare the individual characteristics of homicide offenders across levels of problematic substance use; and (3) compare homicide incident characteristics across levels of problematic substance use.

DESIGN AND SETTING

Observational study using data collected through face-to-face interviews in custodial and community correctional settings across Australia. Participants were recruited through an opt-in process.

PARTICIPANTS

The data consist of 302 individuals convicted of murder or manslaughter.

MEASUREMENTS

We used the Alcohol Use Disorder Identification Test and Drug Abuse Screening Test to determine problematic alcohol or drug use. We also used a range of self-report measures to ascertain offender characteristics [socio-demographics, developmental experiences, criminal history, personality] and incident characteristics (who was killed, and situational intoxication).

FINDINGS

Of the sample, 38.8% displayed high levels of alcohol problems and 30.8% displayed high levels of drug problems. Those displaying high levels of alcohol and/or drug problems were more likely than those without high levels of alcohol and/or drug problems to report adverse developmental experiences, low education, financial difficulties, extensive criminal histories and high levels of trait anger, impulsivity and risk-seeking. In addition, offenders with problematic substance use were more likely to have killed non-family and to have used substances at the time of the homicide.

CONCLUSIONS

High proportions of homicide offenders in Australia appear to have problematic substance use in the year preceding the homicide offence, and such use appears to be associated with a range of other challenging factors, including adverse childhoods, criminal involvement, low socio-economic factors and low self-regulation.

Criminal Careers Among Female Perpetrators of Family and Nonfamily Homicide in Australia

Knowledge of women's pathways to serious offending, including homicide, is limited. This study contributes to a small but growing body of literature examining the criminal careers of serious female offenders by using interview data with females convicted of murder or manslaughter in Australia to examine various dimensions of their criminal careers, specifically, prevalence, frequency, age of onset, duration, and offending variety. In particular, in this study we compared criminal career dimensions across women who had killed a family member (e.g., intimate partner, children) and those whose victims were not part of the family unit (i.e., acquaintances or strangers). Our findings reveal differences between female homicide offenders who kill within and outside of the family unit. Although both groups had comparable overall lifetime prevalence of self-reported participation in criminal offending, findings indicate that participation among the family group was typically at low levels of frequency, of limited duration, and with relatively little variety in categories of offending. The family group also reported lower contact with the criminal justice system compared with the nonfamily group, and were less likely to have experienced some form of criminal/legal sanction in the 12 months prior to the homicide incident. This suggests that women who kill family members are more "conventional" than their nonfamily counterparts, in terms of having low and time-limited (i.e., short duration) lifetime participation in criminal offending.

Exploring the Prevalence and Correlates Associated With Intimate Partner Violence During Pregnancy in Bangladesh

Intimate partner violence (IPV) during pregnancy is known to have multiple detrimental consequences for the woman and potentially for her unborn child. However, little is known about the nature and extent of IPV during pregnancy, particularly in developing countries, which compromises efforts to address the problem. Relying on population-based data, this article examines the extent, patterns, and correlates associated with physical, sexual, and psychological IPV during pregnancy in Bangladesh. Cross-sectional survey data were collected between October 2015 and January 2016 from 426 new mothers, aged 15 to 49 years, who were in the first 6 months postpartum. IPV was assessed with a validated set of survey items. Multivariate logistic regression analyses were conducted to evaluate correlates associated with different types of IPV. Overall, 66.4% of women experienced any IPV during pregnancy. The prevalence of physical, sexual, and psychological IPV was 35.2%, 18.5%, and 65%, respectively. These forms of IPV often overlap, particularly physical and psychological IPV. Pregnant women who report limited social support and have controlling husbands are at significantly increased risk for all three types of IPV during pregnancy. Women who cling to traditional gender roles and those with low self-esteem exhibit increased risk for physical and psychological IPV during pregnancy. Psychological IPV during pregnancy is also correlated with low decision-making autonomy and childhood exposure to violence. Women whose husband's demand a dowry at marriage are at increased risk of sexual IPV during pregnancy. Results reinforce the need to conduct routine screening during pregnancy to identify women with a history of IPV and to be able to offer help and support. The findings also reinforce calls for gender equity and women's equal access to family and social resources thereby increasing women's social support networks, their self-esteem, and autonomy, and reducing their risk of IPV during pregnancy.

Do Maternal Depression and Self-Esteem Moderate and Mediate the Association Between Intimate Partner Violence After Childbirth and Postpartum Suicidal Ideation?

Intimate partner violence (IPV) during the perinatal period is believed to have an adverse effect on maternal mental health. Given the risks of suicide and related public health concerns, the aim of this study is to examine (1) the association of experiencing physical, psychological, and sexual IPV after childbirth on postpartum suicidal ideation (SI), and (2) whether postpartum depression and self-esteem act to mediate or moderate the relationship between IPV and postpartum SI. A cross-sectional survey was conducted from October 2015 to January 2016 in the Chandpur District of Bangladesh among 426 new mothers, aged 15 to 49 years, who were in the first 6 months postpartum. Multivariate logistic regression models were used to examine the association between experiencing IPV and postpartum SI, controlling for a range of other known influences. The prevalence of postpartum SI was 30.8%. Accounting the influence of other confounders, the odds of postpartum SI were significantly higher among women who reported physical IPV victimization (adjusted odds ratio: 2.65; 95% confidence interval = 1.36, 5.18) at any point during the first 6 months following childbirth as opposed to those who did not. In addition, postpartum depression increased postpartum SI, while high self-esteem significantly reduced reports of SI. Both postpartum depression and maternal self-esteem notably mediate and moderate the effect of physical IPV after childbirth on postpartum SI. The findings illuminate that IPV victimization after childbirth significantly increases the odds of postpartum SI. This study reinforces the need to detect women with a history of IPV who may be at risk for SI, not only to offer them help and support but also to prevent or reduce SI.

Does the type of maltreatment matter? Assessing the individual and combined effects of multiple forms of childhood maltreatment on exclusive breastfeeding behavior

BACKGROUND

Childhood maltreatment (CM) has been associated with a range of adult health outcomes; however, extant research has focused more on exposure to a single form of abuse rather than multiple forms. Moreover, very few studies have specifically investigated the impact of CM on exclusive breastfeeding (EBF) outcomes.

OBJECTIVES

This study aims to examine: (1) the individual and combined effects of multiple forms of CM on EBF outcomes; and (2) whether postpartum depression and maternal stress act to mediate or moderate the association between CM and EBF.

METHOD

Cross-sectional survey data were collected between October 2015 and January 2016 from 426 women of Bangladesh who were six months postpartum.

RESULTS

Based on the adjusted multivariate logistic regression model, women who experienced childhood sexual abuse (CSA) were significantly less likely to exclusively breastfeed babies than their non-abused counterparts (AOR: 0.38, 95% CI [0.15, 0.92]). When a composite measure was created to examine the additive effects of adverse childhood experiences, a dose-response association was observed between the reported number of different types of CM and early termination of EBF. Though experiencing postpartum depression and maternal stress do not mediate the effect of CSA on EBF, they do moderate them such that the odds of early termination of EBF are notably higher among women who experienced CSA in combination with postpartum depression or high levels of stress.

CONCLUSIONS

Findings from this study offer some insight into the intergenerational effects associated with CM experiences, and underpin the need for effective policies and programs to prevent or reduce its occurrence and improve the EBF outcomes.

Oncological and functional outcomes of trans-oral robotic surgery for pyriform sinus carcinoma: A French GETTEC group study

BACKGROUND

Pyriform sinus carcinomas (SCC) present specific functional and oncological issues. The recent advent of trans-oral robotic surgery (TORS), as a conservative procedure, has opened up new perspectives.

OBJECTIVES

To present the oncological and functional outcomes of TORS for pyriform sinus SCC.

MATERIALS AND METHODS

We included, retrospectively, all TORS procedures for pyriform sinus SCC performed between 2009 and 2017 in eight French tertiary referral centers. We excluded lesions involving the pyriform sinus that had developed from the oropharynx, larynx, or other anatomic sub-sites of the hypopharynx.

RESULTS

We included 57 TORS procedures. Median hospital stay was 10 days. A preventive tracheotomy was performed in seven cases (12%), and all were successfully decannulated. Oral re-feeding was possible for 93%, after a median of 5 days. The main surgical complications were hemorrhages (three cases), all successfully handled, although 2 patients with heavy comorbidities died from blood loss in the days after. Adjuvant therapy was proposed in 31 cases (54%), including two cases of salvage surgery (total pharyngolaryngectomy). After a median follow-up of 23 months, overall and disease-free survival were, respectively, 84% and 74% at 24 months, and 66% and 50% at 48 months. At the end of follow-up, organ preservation rate was 96%. None of the surviving patients needed a tracheotomy and oral diet was possible for 96%.

CONCLUSION

The functional and oncological outcomes of TORS for pyriform sinus cancer are encouraging, and this procedure can be considered safe for selected early or moderately advanced cases as a conservative treatment.

Factors associated with child protection recurrence in Australia

The aim of the current research was to advance understanding of child protection in Australia by examining the factors associated with recurrence of child protection notifications to the formal child protection system. Extant research has been primarily undertaken in the USA and it is important to understand whether similar factors associated with recurrence actually hold in the Australian context. Administrative data were obtained for a sample of 9608 children first subject to a screened-in report in 2011-12. Children were followed for 12 months. Cox Proportional Hazard models were used to measure associations between 26 independent variables and four types of recurrence: subsequent reports, subsequent investigations, subsequent substantiations, and subsequent intervention. Factors associated with recurrence in Australia were broadly similar to those identified in other jurisdictions, including reports and substantiation for neglect, younger age, prior child protection involvement in the household, and parental characteristics including drug use, mental health problems, and history of maltreatment as a child. As in previous studies, post-investigative service provision was positively associated with recurrence. In prior US research, race did not predict recurrence. However, in the present study, Indigenous Australian children were significantly more likely to be subject to all types of recurrence measured. Future research on recurrence should aim to disentangle the complex relationships between child protection recurrence, child maltreatment, and service delivery. Recurrence is not a good proxy indicator of child safety. The findings have implications for the equity of recurrence-based risk assessment tools as they are applied to indigenous populations.

Characteristics of Homicide-Suicide in Australia: A Comparison With Homicide-Only and Suicide-Only Cases

Homicide-suicide represents one of the rarest forms of lethal violence but often precipitates calls to revise social, health, and justice policies. However, there is little empirical information about this type of violence. The current study uses two unique data sets to examine a wide range of individual and situational characteristics of homicide-suicide, with particular emphasis on establishing whether and how homicide-suicide differs from homicide-only and suicide-only. Findings suggest homicide-suicide may have unique characteristics that set it apart from both homicide-only and suicide-only, as well as sharing certain other characteristics with those two types of events.

Intimate partner violence around the time of pregnancy and postpartum depression: The experience of women of Bangladesh

BACKGROUND AND OBJECTIVES

Intimate partner violence (IPV) around the time of pregnancy is a serious public health concern and is known to have an adverse effect on perinatal mental health. In order to craft appropriate and effective interventions, it is important to understand how the association between IPV and postpartum depression (PPD) may differ as a function of the type and timing of IPV victimization. Here we evaluate the influence of physical, sexual and psychological IPV before, during and after pregnancy on PPD.

METHODS

Cross-sectional survey data was collected between October 2015 and January 2016 in the Chandpur District of Bangladesh from 426 new mothers, aged 15-49 years, who were in the first six months postpartum. Multivariate logistic regression models were used to estimate the association between IPV and PPD, adjusted for socio-demographic, reproductive and psychosocial confounding factors.

RESULTS

Approximately 35.2% of women experienced PPD within the first six months following childbirth. Controlling for confounders, the odds of PPD was significantly greater among women who reported exposure to physical (AOR: 1.79, 95% CI [1.25, 3.43]), sexual (AOR: 2.25, 95% CI [1.14, 4.45]) or psychological (AOR: 6.92, 95% CI [1.71, 28.04]) IPV during pregnancy as opposed to those who did not. However, both before and after pregnancy, only physical IPV evidences a direct effect on PPD. Results highlight the mental health consequences of IPV for women of Bangladesh, as well as the influence of timing and type of IPV on PPD outcomes.

CONCLUSIONS AND IMPLICATIONS

The findings confirm that exposure to IPV significantly increases the odds of PPD. The association is particularly strong for physical IPV during all periods and psychological IPV during pregnancy. Results reinforce the need to conduct routine screening during pregnancy to identify women with a history of IPV who may at risk for PPD and to offer them necessary support.

The complexity of child protection recurrence: The case for a systems approach

OBJECTIVE

Research on child protection recurrence has found consistent child, family, and case characteristics associated with repeated involvement with the child protection system. Despite the considerable body of empirical research, knowledge about why recurrence occurs, and what can be done to reduce it, is limited.

METHOD

This paper reviews the empirical literature and analyses the approaches of prior recurrence research. Four related conceptual challenges are identified: (1) a tendency to conflate child protection recurrence with repeated child maltreatment; (2) uncertainty about how best to operationalize and measure child protection recurrence in research; (3) inconsistency between prevailing explanations for the most frequently observed patterns of recurrence; and (4) difficulty in developing coherent strategies to address child protection recurrence based on research.

RESULTS

Addressing these challenges requires a greater consideration of the effects of decision-making in the child protection system on recurrence. This paper proposes a methodology based in systems theory and drawing on existing administrative data to examine the characteristics of the child protection system that may also produce recurrence.

A cycle of violence? Examining family-of-origin violence, attitudes, and intimate partner violence perpetration

Exposure to violence in the family-of-origin has consistently been linked to intimate partner violence (IPV) perpetration in adulthood. However, whether the transmission of violence across generations is role- and gender-specific still remains unclear. The current study examined the effects of experiencing child abuse and observing parental violence on IPV perpetration among a sample of male arrestees (N = 303). The differential effects of observing violence perpetrated by same-sex (father to mother), opposite-sex (mother to father), and both parents on subsequent IPV perpetration were examined. Logistic regression analyses showed that while observing father-only violence and bidirectional interparental violence was predictive of IPV perpetration, observing mother-only violence and direct experiences of child abuse was not. These findings suggest that the transmission of violence across generations is both role- and gender-specific and highlight the importance of examining unique dimensions of partner violence to assess influences on children. The study further examined whether attitudes justifying wife beating mediate the effect of exposure to violence and subsequent IPV perpetration. Results showed that although attitudes were predictive of perpetration, these attitudes did not mediate the relationship.

Community knowledge, attitudes and behaviours about environmental tobacco smoke in homes and cars

OBJECTIVE

to assess knowledge, attitudes and behaviours about environmental tobacco smoke (ETS) in cars and homes in Queensland.

METHOD

1,026 randomly selected Queensland residents (84% response) participated in a computer assisted telephone survey to assess knowledge, attitudes and behaviours about ETS in cars and homes; and attitudes towards restrictions on smoking in a range of contexts.

RESULTS

Most respondents are aware of the negative health effects of ETS and have smoking bans in their cars (75.8%) and homes (76.8%), however bans are less prevalent for smokers (cars: 37.9%; homes: 51%; p=0.000). For cars/homes, most smokers who did not have smoking bans would not smoke at all around pregnant women (67.7%/53.7%); fewer would refrain for children<or=12 years (48.2%/35.1%); non-smoking adults (31.3%/17.9%); and children 13-17 years (30.9%/21.2%). Parent smokers are less likely to not smoke at all around children>or=2 years (p=0.000) compared to non-parent smokers. Most respondents support car/ home smoking bans for children<or=12 years (80.5%/66.1%); children 13-17 years (78.2%/64.7%); and pregnant women (80.5%/67%).

CONCLUSIONS

There is strong community support for legislation targeting ETS in cars and homes, however this varies by context, smoking and parental status.

Heterogeneity in the association between social-emotional adjustment profiles and deviant behavior among male and female serious juvenile offenders

This article examines the relation among gender, social-emotional adjustment, and deviant behavior among serious juvenile offenders. A sample of 105 adolescent offenders completed questionnaires assessing social-emotional characteristics and self-reported involvement in deviant behaviors. Results indicate significant associations between distress and restraint in predicting deviance, a finding that was invariant across gender. Analysis of four distinct social-emotional profiles found that membership in the reactive group was associated with the greatest amount of deviant behavior. Results also indicate that not only do serious offending girls internalize more than serious offending boys, they appear equally likely to externalize. However, although boys exhibit less distress than girls, those boys who report high rates of deviance may exhibit internalizing and externalizing problems similar to girls. The use of social-emotional measures in general, and distinct profiles in particular, may aid in targeting specific programming and treatment in an effort to provide offenders with more effective interventions.

Sex differences in empathy and its relation to juvenile offending

Implicit in most theoretical accounts of sex differences in offending is the assumption that females are less likely than males to engage in crime--especially serious, violent crime--in part because of their comparatively higher levels of concern for others and stronger affiliative ties. Much research suggests that significant sex differences in both empathy and serious offending emerge in adolescence, with females displaying notably higher levels of empathy and males engaging in notably higher levels of serious offending. However, there has been little empirical work assessing the degree to which sex differences in empathy among adolescents can account for sex differences in offending. This research uses data from a sample of adolescents attending public high schools in Philadelphia (n = 425) and a sample of adolescents incarcerated in the California Youth Authority (CYA) (n = 232) to examine the relation between empathy and serious offending. Results suggest that empathy acts as a protective factor for both males and females but that there are subtle differences among males and females in the relation between empathy and offending.

A cluster-analytic investigation of MMPI profiles of serious male and female juvenile offenders

OBJECTIVE

To use cluster analysis to identify psychological profiles and related mental health symptoms among male and female juvenile offenders.

METHOD

Juvenile offenders (N = 141) incarcerated in the California Youth Authority completed the Minnesota Multiphasic Personality Inventory (MMPI) and the Massachusetts Youth Screening Instrument-Version 2 (MAYSI-2).

RESULTS

MMPI cluster analysis revealed four distinct profiles: two for male and two for female juvenile offenders. Among males, we identified one Normative cluster with no clinically elevated scores. A second male cluster, labeled Disorganized, exhibited clinical elevations on scales 8 (Schizophrenia), 6 (Paranoia), 4 (Psychopathic Deviate), and 7 (Psychasthenia). Among females, two clinically elevated profiles emerged. One Impulsive-Antisocial cluster consisted of clinical elevations on scale 4 (Psychopathic Deviate), which has been consistently associated with delinquent and antisocial behavior. The second cluster, labeled Irritable-Isolated, produced elevations on MMPI scales 4 (Psychopathic Deviate), 8 (Schizophrenia), 6 (Paranoia), and 7 (Psychasthenia). There were no significant sex, ethnicity, or offense differences across clusters, but the clusters exhibit distinct psychiatric profiles (MMPI) and mental health symptoms (MAYSI-2).

CONCLUSIONS

The findings indicate that not only do female offenders have more acute mental health symptoms and psychological disturbances than male offenders, they exhibit qualitatively distinct psychiatric profiles. Results reinforce the need for assessment of mental health symptoms for male and female juvenile offenders as well as sex-appropriate treatments.

Violent responses to strain: an examination of conditioning influences

Past research on General Strain Theory (GST) has not widely examined the application of the theory for understanding violent responses to strain. Additionally, the theory suggests there may be varying effects of strain on possible deviant outcomes across individuals differentiated on their dispositions toward deviance. In the current analysis, we examine violent responses to strain using original data collected from a sample of college-aged youth. Moreover, we specifically examine whether the effects of strain and anger on possible violent outcomes are invariant across individuals differentiated on their level of exposure to deviant peers and moral constraints against deviance. Using structural equation modeling, our results suggest that a composite measure of strain increases respondents' intentions to engage in assaultive behavior net of other predictors. Additionally, the results reveal that anger mediates the impact of strain on possible violent responses. Finally, the results of our subgroup analyses suggest that the basic form of the GST model is invariant across groups.