Kim and Ruger BMC Public Health 2010, 10:195 http://www.biomedcentral.com/1471-2458/10/195 showed little health difference, although odds ratios between groups increased significantly after controlling for behavioral risk factors. Efforts to reduce health dis- parities in South Korea require attention to the root causes of socioeconomic inequality and especially to the gender differences in the impact of socioeconomic posi- tion on health. Additional material Additional file 1 Appendix A. Korean Occupational Classification Index. Competing interests The authors declare that they have no competing interests. Authors' contributions HK contributed to the conception and design of this study, undertook data analyses and interpretation and wrote the original draft. JR contributed to the conception and design of the study and contributed to revising the manu- script. All authors have read and approved the final manuscript. Acknowledgements Dr. Ruger is supported in part by a Career Development Award from the U.S. National Institutes of Health (grant K01DA016358) and an Investigator Award from the Patrick and Catherine Weldon Donaghue Medical Research Founda- tion (grant DF06-112). Dr. Kim was funded in part by the Korea National Research Foundation (grant KRF-003-B00142). We thank the Whitney and Betty MacMillan Center for International and Area Studies and the Luce Foundation for financial support. We thank Keeho Lee of the Korea Gallop Organization and Sungjin Ahn and Yunsung Chung of the Deaprtment of Statistics at Gyeo- ngsang National University for data clarification and technical assistance. We thank Nora Ng and Christina Lazar for editing and research assistance. Author Details 1Dongguk University, Department of Social Welfare, Seoul, Republic of Korea and 2Yale University Schools of Medicine and Public Health, Division of Health Policy and Administration, New Haven, CT, USA Received: 9 October 2009 Accepted: 15 April 2010 Published: 15 April 2010 TB©hM2isC0ia1Psr0utaibKncliemOcHipsaenavdlAathRiclua2gbe0sl1er0;fa,lrio1ctme0icnl1:esh9ed5teispBt:ri/obwMuwetdwC.bueinodmtraerldtLhctedn.etraml.csomft/h1e47C1re-2a4ti5v8e/C10o/m19m5onsAtributionLicense(htp:/creativecommons.org/licenses/by/2.0),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited. References 1. Kahn RS, Wise PH, Kennedy BP, Kawachi I: State income inequality, household income, and maternal mental and physical health: cross sectional national survey. BMJ 2000, 321:1311-1315. 2. Sturm R, Gresenz CR: Relations of income inequality and family income to chronic medical conditions and mental health disorders: national survey. 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