This research is supported by the social science planning and cultivation project of chongqing under grant No.2014PY50 and the humanities and social science
research project of chongqing municipal education commission under grant No. 15SKG131. This research is supported by the fundamental and advanced research projects of chongqing under grant No. CSTC2013JCYJA40039 and the national statistical science research project under grant No. 2015LZ22.