BRITISH JOURNAL OF PSYCHIATRY (2006), 189, 465^466. doi: 10.1192/bjp.bp.106.021816 SHORT REPORT

The ecological fallacy and the gender ratio urban and rural populations. The values of the test statistics for assessing the homo- of in geneity were 186.48 and 3070.10 (com- pared with a critical value of 5.226, d.f.d.f.¼12) for the age-specific urban and PAUL S. F.F.YIP YIP and KAKAY. Y. LIU rural gender ratios respectively. The very small probability value is in contradiction to the homogeneity assumption among the ratios for age-groups and region. The lower panel of Fig. 1 shows the age-specific male/ female ratios of suicide in urban and rural areas: in urban areas the suicide rates Summary China is the only country in METHOD among those under 30 years old were which the suicide rate is higher among slightly higher among women than men, We examined the gender ratio of in but among themiddle-aged and elderly womenthanwomen than men. WeprovideWe provide a China using the most recent mortality groups the male/femalemale/female ratios were close demographic perspective on the gender statistics (1991–2001) provided by China’s to or larger than 1. In rural areas, women differential in suicide in China.This shows Ministry of Health. The Ministry’s mortal- also did not universally have higher suicide that the male/female ratio of suicide ity registry is based on a 10% sample of the rates across all age-groups. Male suicides increased betweenbetween1991and 1991 and 202001and 01 and Chinese population, and it is the only sys- were more prevalent among those over 60 tem in China to record causes of deaths years old, and across the age-groups only there is reason to believe this trend will annually for a population of 1.3 billion. women in rural areas aged 20–34 years continue. Among the population In 2000 over 60% of the population lived had higher suicide rates than their male subgroups, only young women living in in rural areas (Zhou & Ma, 2003) and counterparts. rural areas had much higher suicide rates the rural regions are economically deprived in comparison with their urban counter- thantheirthan their male counterparts.Itiscounterparts.It is argued parts. We projected the data on suicide DISCUSSION that consideration of the gender ratio of rates from the Ministry of Health to the suicide in China mustmusttake take age-, gender- age-, gender- and region-specific popu- The ‘ecological fallacy’ refers to the and region-specific suicide patterns and lation statistics of the Chinese Bureau of thinking that what is true at the aggregate the population structure into account.The Statistics to adjust for the effect of the level must be true at the individual level. population distribution on the overall One simple explanation of international increasing urbanisation of China islikely to male/female ratio of suicide (for further differences in suicide rates, as stated in be associated with more male suicides and details of the suicide rates and our Moksony’s composition theory (Moksony, we predictthat before long the male projection method, see Yip et aletal, 2005,2005aa).). 1990), is that the countries’ populations suicidesuicideratewillovertakethatoffemales. rate willovertake thatof females. differ in the proportions of those at risk of suicide. China’s population is still Declaration of interest None.None. RESULTSRESULTS skewed towards the younger cohorts: men and women aged below 40 years accounted The male/female ratio of suicide is about 4 We found that the male/female ratio of for 68% of the total population in 2001. in Western countries such as Australia, the suicide had been increasing from 1991 to Over 60% of the population lives in rural USAUSAandand the UK. In Asian countries, for ex- 2001; in 1991 the ratio was 0.78 and in areas (Zhou & Ma, 2003). Our results have ample India and Hong Kong (Yip et aletal,, 2001 it was 0.91. The upper panel of shown that the male/female ratios of 2000), this ratio is often less than 2 (Mayer Fig. 1 gives suicide rates by age, gender suicide were not uniform across the popu- & Ziaian, 2002; World Health Organiza- and region for China in 2001. It shows that lation subgroups. It was this population tion, 2002). China is reportedly the only suicide rates increased with age; a distinct structure and the high suicide rates among country in the world in which the suicide rate peak was observed among women living young women in rural areas that led to a is higher among women than men (Pritchard, in rural areas in the age range 25–34 years; male/female ratio of less than 1 at theatthe 1996). This unique pattern has attracted and rural suicide rates were higher than national level. Such unique patterns of sui- much attention, but little is known about urban rates across all age-groups. cide rates and demographic characteristics its underlying causes (Yip, 1996). WeWe Although China’s overall male/female must be taken into account when inter- suggest that a demographic perspectiveperspective ratio of suicide was still less than 1 in preting the male/female ratio of suicide in could shed light on the low male/femalemale/female ratio 2001, closer examination revealed that this China. Otherwise, it may be misleading to of suicide in China. In particular, we exam- was mostly the result of the high suicide suggest that women are more likely to die ine whether Chinese women in different rate in one particular population subgroup, by suicide than menin China by referring population subgroups have uniformly namely young women aged 20–34 years to the low male/femalemale/female ratio of suicide at higher risk than their male counterparts, living in rural areas. The Woolf test (Woolf, the national level. and discuss how the national male/female 1955), which is essentially a ww22 test, wastest,was China has undergone rapid demo- ratio of suicide may be affected by the used to test the homogeneity of the male/ graphic changes in the past two decades demographic changes taking place in China. female ratios across all age-groups for the and these changes would affect the overall

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male/female ratio of suicide. First, probably PAUL S. F.YIP,PhD, Hong Kong Jockey Club Centre for Suicide Research and Prevention and Department of because of the ‘one child’ policy which has Statistics and Actuarial Science,UniversityScience, , Hong Kong;KAKong; KA Y. LIU,MPhil,LIU, MPhil, Hong Kong Jockey been enforced since 1980, China is facing Club Centre for Suicide Research and Prevention,UniversityPrevention, University of Hong Kong, Hong Kong and Nuffield College, an acute problem of ageing. According to University of Oxford,Oxford,UK UK the Chinese Bureau of Statistics, the total fertility rate has fallen from more than 3 CorrespCorrespondence:ondence: Paul S.F.Yip,HongS. F.Yip, Hong Kong Jockey Club Centre for SuSuicideicide Research and Prevention, before 1980 to 1.8 in 2002, which is below University of Hong Kong,Kong,Hong Hong Kong.Tel: +852 2241 6013; fax: +852 2549 7161; email: sfpyip@@hku.hkhku.hk the replacement level of 2.1 (Chan et aletal,, (First received 19 January 2006, final revision 15 April 2006, accepted 2 May 2006) 2002). The proportion of the population over 65over65will rise to the levels of most Western countries by 2025 (Hesketh & come to resemble more those ratios of (Chan(Chan et aletal, 2005; Yip et aletal, 2005,2005bb); it re-re-);it Zhu, 1997). Second, the gender imbalance Western countries. mains to be seen whether the rate of suicide at birth is now amounting to a male/female What is left unanswered is how other by charcoal burning will increase in main- ratio of 1.15in some districts, deviating between-country differences may explain land China and change the pattern of substantially from the norm of 1.05 the gender patterns of suicide in East and suicide there. Further research is needed to (Hesketh & Zhu, 1997). The effects of the West. One such difference may lie in the explore other possible explanations, such ‘one child’ policy are beginning to have a availability of pesticides. Young women in as cultural attitudes towards gender roles, severe impact on the population distri- most countries tend to have high rates of the meaning of suicide and the prevalence bution: the proportion in the age-group attempting suicide, but easy access to pesti- of mental illness among both men and 20–39 years will shrink (Chan et aletal,, cide and rat poison in rural areas of China women in rural and urban communities. 2002). Third, urbanisation is rapidly taking may account for the high fatality rate. In place: Zhou & Ma (2003) estimated that fact, 62% of suicide deaths in China re- REFERENCES China’s urbanisation level rose from 26% sulted from ingestion of pesticide or rat Chan, C. L.,Yip, P. S. F., Ng, E. H., et aletal (2002)(2002) to 36%to36%between 1990 and 2000. Owing poison (Phillips et aletal, 2002). Such easy Gender selection in China: its meanings and to these demographic changes, the size of availability of highly lethal substances implications. Journal of Assisted Reproduction and the female population in the 20–39 age may explain the high suicide rates among GeneticsGenetics,, 1919, 426^430. range living in rural areas will decline rural women. However, the rapid increase Chan,Chan,K.P.M.,Yip,P.S.F.,Au,J., K. P. M.,Yip, P. S. F., Au, J., et aletal (2005) rapidly in the next few decades. This is ex- of charcoal-burning suicides among Charcoal-burning suicide in post-transition Hong Kong. British Journal of Psychiatry,, 186186, 67^73.,67^73. pected to increase the male/female ratio of middle-aged menin Hong Kong has led suicide at the national level, which will to a higher male/femalemale/female ratio of suicide Hesketh,T.Hesketh, T. & Zhu,W.X.(19 (1997) 9 7) . The one child family policy: the good, the bad, and the ugly. BMJBMJ,, 314314,1685^1687.

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