An Econometric Analysis of Hospital Length of Stay for Cataract Operations in Japan by the Box-Cox Transformation Model and Hausman Tests: Evaluation of the 2010 Revision of the Medical Payment System*
Affiliation(s)
1 Graduate School of Engineering, University of Tokyo, Tokyo, Japan. 2 Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
1 Graduate School of Engineering, University of Tokyo, Tokyo, Japan. 2 Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
ABSTRACT
The Japanese medical costs for cataract treatments reached 270 billion yen in fiscal year 2012. Since the length of stay (LOS) in hospital is much longer than other major countries, controlling the medical costs by reducing LOS becomes an important issue in Japan. In this paper, we evaluated the effects of the 2010 revision of the Japanese medical payment system (DPC/PDPS) on LOS for cataract operations. The Box-Cox transformation model, Nawata’s estimators and Hausman tests were used in the analysis. To evaluate the effects, we analyzed a dataset obtained from 34 DPC hospitals (Hp1-34) where one-eye cataract operations were performed both before (April 2008-March 2010) and after (April 2010-March 2012) the 2010 revision and there were more than 500 patients. The dataset contained information from 32,593 patients. We did not admit the effect of the 2010 revision in this study, and there were large differences LOS among hospitals, even after removing the influences of factors such as patient characteristics and types of principal diseases.
The Japanese medical costs for cataract treatments reached 270 billion yen in fiscal year 2012. Since the length of stay (LOS) in hospital is much longer than other major countries, controlling the medical costs by reducing LOS becomes an important issue in Japan. In this paper, we evaluated the effects of the 2010 revision of the Japanese medical payment system (DPC/PDPS) on LOS for cataract operations. The Box-Cox transformation model, Nawata’s estimators and Hausman tests were used in the analysis. To evaluate the effects, we analyzed a dataset obtained from 34 DPC hospitals (Hp1-34) where one-eye cataract operations were performed both before (April 2008-March 2010) and after (April 2010-March 2012) the 2010 revision and there were more than 500 patients. The dataset contained information from 32,593 patients. We did not admit the effect of the 2010 revision in this study, and there were large differences LOS among hospitals, even after removing the influences of factors such as patient characteristics and types of principal diseases.
KEYWORDS
Diagnosis Procedure Combination (DPC), Cataract, Length of Stay (LOS), Box-Cox Transformation Model
Diagnosis Procedure Combination (DPC), Cataract, Length of Stay (LOS), Box-Cox Transformation Model
Cite this paper
Nawata, K. and Kawabuchi, K. (2015) An Econometric Analysis of Hospital Length of Stay for Cataract Operations in Japan by the Box-Cox Transformation Model and Hausman Tests: Evaluation of the 2010 Revision of the Medical Payment System*. Open Journal of Applied Sciences, 5, 559-570. doi: 10.4236/ojapps.2015.59054.
Nawata, K. and Kawabuchi, K. (2015) An Econometric Analysis of Hospital Length of Stay for Cataract Operations in Japan by the Box-Cox Transformation Model and Hausman Tests: Evaluation of the 2010 Revision of the Medical Payment System*. Open Journal of Applied Sciences, 5, 559-570. doi: 10.4236/ojapps.2015.59054.
References
[1] DPC Evaluation Division, Central Social Insurance Medical Council (2010) Heisei 24 nendo kaite ni muketa DPC seido (DPC/PDPS) no taiou ni tsuite (Concerning the Procedures for the 2012 Revision of the DPC System (DPC/PDPS)). (In Japanese) [2] DPC Evaluation Division, Central Social Insurance Medical Council (2013) DPC taishou hyouin junbi hyouin no gennjou ni tsuite (Current Situations of DPC Hospitals and Preparing Hospitals). (In Japanese) [3] Nawata, K., Ii, M., Toyama, H. and Takahashi, T. (2009) Evaluation of the Inclusive Payment System Based on the Diagnosis Procedure Combination with Respect to Cataract Operations in Japan. Health, 1, 93-103. http://dx.doi.org/10.4236/health.2009.12016 [4] Nawata, K. and Kawabuchi, K. (2015) Evaluation of Length of Hospital Stay Joining Educational Programs for Type 2 Diabetes Mellitus Patients: Can We Control Medical Costs in Japan?” Health, 7, 256-269.
http://dx.doi.org/10.4236/health.2015.72030 [5] Ministry of Health, Labour and Welfare (2014) Hesiei 24 nendo kokumin iryouhi no gaikyou (Summaries of National Medical Expenditures in Fiscal Year 2012). (In Japanese) [6] Ministry of Health, Labour and Welfare (2013) Shakai iryou shinryu koui betsu chosa hesiei 24 nendo (Social Medical Surveys by Treatment Practices in Fiscal Year 2012). (In Japanese) [7] OECD (2013) Health at a Glance 2013.
http://www.oecd-ilibrary.org/social-issues-migration-health/data/oecd-health-statistics_health-data-en [8] Box, G.E.P. and Cox, D.R. (1964) An Analysis of Transformations. Journal Royal Statistical Society Series B, 26, 211- 252. [9] Nawata, K. (2013) A New Estimator of the Box-Cox Transformation Model Using Moment Conditions. Economics Bulletin, 33, 2287-2297. [10] Nawata, K. (2015) Robust Estimation Based on the Third-Moment Restriction of the Error Terms for the Box-Cox Transformation Model: An Estimator Consistent under Heteroscedasticity. Economics Bulletin, 3, 1056-1064. [11] Hossain, M.Z. (2011) The Use of Box-Cox Transformation Technique in Economic and Statistical Analyses. Journal of Emerging Trends in Economics and Management Sciences, 2, 32-39. [12] Sakia, R.M. (1992) The Box-Cox Transformation Technique: A Review. The Statistician, 41, 169-178.
http://dx.doi.org/10.2307/2348250 [13] Amemiya, T. and Powell, J.L. (1981) A Comparison of the Box-Cox Maximum Likelihood Estimator and the Non- Linear Two Stage Least Squares Estimator. Journal of Econometrics, 17, 351-381.
http://dx.doi.org/10.1016/0304-4076(81)90007-5 [14] Yang, Z. (2006) A Modified Family of Power Transformations. Economics Letters, 92, 14-19.
http://dx.doi.org/10.1016/j.econlet.2006.01.011 [15] Yeo, I.K. and Johnson, R.A. (2000) A New Family of Power Transformation to Improve Normality or Symmetry. Biometrika, 87, 954-959. http://dx.doi.org/10.1093/biomet/87.4.954 [16] Showalter, M.H. (1994) A Monte Carlo Investigation of the Box-Cox Model and a Nonlinear Least Squares Alternative. Review of Economics and Statistics, 76, 560-570. http://dx.doi.org/10.2307/2109980 [17] Bickel, P.J. and Doksum, K.A. (1981) An Analysis of Transformations Revisited. Journal of American Statistical Association, 76, 296-311. http://dx.doi.org/10.1080/01621459.1981.10477649 [18] Powell, J.L. (1996) Rescaled Method-of-Moments Estimation for the Box-Cox Regression Model. Economics Letters, 51, 259-265. http://dx.doi.org/10.1016/0165-1765(96)00811-7 [19] Hausman, J. (1978) Specification Test in Econometrics. Econometrica, 46, 1251-1272.
http://dx.doi.org/10.2307/1913827 [20] Nawata, K. and McAleer, M. (2014) The Maximum Number of Parameters for the Hausman Test When the Estimators Are from Different Sets of Equations. Economic Letters, 123, 291-294.
http://dx.doi.org/10.1016/j.econlet.2014.03.005 [21] Nawata, K. and Kawabuchi, K. (2015) Financial Sustainability of the Japanese Medical Payment System: Analysis of the Japanese Medical Expenditure for Educational Hospitalization of Patients with Type 2 Diabetes. Health, 7, 1007- 1021. http://dx.doi.org/10.4236/health.2015.78118
[1] DPC Evaluation Division, Central Social Insurance Medical Council (2010) Heisei 24 nendo kaite ni muketa DPC seido (DPC/PDPS) no taiou ni tsuite (Concerning the Procedures for the 2012 Revision of the DPC System (DPC/PDPS)). (In Japanese) [2] DPC Evaluation Division, Central Social Insurance Medical Council (2013) DPC taishou hyouin junbi hyouin no gennjou ni tsuite (Current Situations of DPC Hospitals and Preparing Hospitals). (In Japanese) [3] Nawata, K., Ii, M., Toyama, H. and Takahashi, T. (2009) Evaluation of the Inclusive Payment System Based on the Diagnosis Procedure Combination with Respect to Cataract Operations in Japan. Health, 1, 93-103. http://dx.doi.org/10.4236/health.2009.12016 [4] Nawata, K. and Kawabuchi, K. (2015) Evaluation of Length of Hospital Stay Joining Educational Programs for Type 2 Diabetes Mellitus Patients: Can We Control Medical Costs in Japan?” Health, 7, 256-269.
http://dx.doi.org/10.4236/health.2015.72030 [5] Ministry of Health, Labour and Welfare (2014) Hesiei 24 nendo kokumin iryouhi no gaikyou (Summaries of National Medical Expenditures in Fiscal Year 2012). (In Japanese) [6] Ministry of Health, Labour and Welfare (2013) Shakai iryou shinryu koui betsu chosa hesiei 24 nendo (Social Medical Surveys by Treatment Practices in Fiscal Year 2012). (In Japanese) [7] OECD (2013) Health at a Glance 2013.
http://www.oecd-ilibrary.org/social-issues-migration-health/data/oecd-health-statistics_health-data-en [8] Box, G.E.P. and Cox, D.R. (1964) An Analysis of Transformations. Journal Royal Statistical Society Series B, 26, 211- 252. [9] Nawata, K. (2013) A New Estimator of the Box-Cox Transformation Model Using Moment Conditions. Economics Bulletin, 33, 2287-2297. [10] Nawata, K. (2015) Robust Estimation Based on the Third-Moment Restriction of the Error Terms for the Box-Cox Transformation Model: An Estimator Consistent under Heteroscedasticity. Economics Bulletin, 3, 1056-1064. [11] Hossain, M.Z. (2011) The Use of Box-Cox Transformation Technique in Economic and Statistical Analyses. Journal of Emerging Trends in Economics and Management Sciences, 2, 32-39. [12] Sakia, R.M. (1992) The Box-Cox Transformation Technique: A Review. The Statistician, 41, 169-178.
http://dx.doi.org/10.2307/2348250 [13] Amemiya, T. and Powell, J.L. (1981) A Comparison of the Box-Cox Maximum Likelihood Estimator and the Non- Linear Two Stage Least Squares Estimator. Journal of Econometrics, 17, 351-381.
http://dx.doi.org/10.1016/0304-4076(81)90007-5 [14] Yang, Z. (2006) A Modified Family of Power Transformations. Economics Letters, 92, 14-19.
http://dx.doi.org/10.1016/j.econlet.2006.01.011 [15] Yeo, I.K. and Johnson, R.A. (2000) A New Family of Power Transformation to Improve Normality or Symmetry. Biometrika, 87, 954-959. http://dx.doi.org/10.1093/biomet/87.4.954 [16] Showalter, M.H. (1994) A Monte Carlo Investigation of the Box-Cox Model and a Nonlinear Least Squares Alternative. Review of Economics and Statistics, 76, 560-570. http://dx.doi.org/10.2307/2109980 [17] Bickel, P.J. and Doksum, K.A. (1981) An Analysis of Transformations Revisited. Journal of American Statistical Association, 76, 296-311. http://dx.doi.org/10.1080/01621459.1981.10477649 [18] Powell, J.L. (1996) Rescaled Method-of-Moments Estimation for the Box-Cox Regression Model. Economics Letters, 51, 259-265. http://dx.doi.org/10.1016/0165-1765(96)00811-7 [19] Hausman, J. (1978) Specification Test in Econometrics. Econometrica, 46, 1251-1272.
http://dx.doi.org/10.2307/1913827 [20] Nawata, K. and McAleer, M. (2014) The Maximum Number of Parameters for the Hausman Test When the Estimators Are from Different Sets of Equations. Economic Letters, 123, 291-294.
http://dx.doi.org/10.1016/j.econlet.2014.03.005 [21] Nawata, K. and Kawabuchi, K. (2015) Financial Sustainability of the Japanese Medical Payment System: Analysis of the Japanese Medical Expenditure for Educational Hospitalization of Patients with Type 2 Diabetes. Health, 7, 1007- 1021. http://dx.doi.org/10.4236/health.2015.78118