This work was supported by the China-WHO Biennial Collaborative Projects 2014-2015, under the project name “Research on the Monitoring, Evaluation, and Improvement of National Medical Service in China” (WHO reference 2014/435380-0; responsible department: Bureau of Medical Administration and Medical Service Supervision, National Health and Family Planning Commission; implementing unit: China Standard Medical Information Research Center); the National Key Technology R&D Program of the Ministry of Science and Technology (2011BAI10B01); and the Beijing Science and Technology Committee (D131100004713007).