{"ok": true, "tool": "explain_missingness", "variables": [{"variable_id": "var_0309", "index": 309, "variable_name": "空气污染指数", "column_name": "环境保护_CIE_201909006_空气污染指数", "original_variable_name": "CIE_2019_09_7002927901_空气污染指数", "source": "CIE_10.19581/j.cnki.ciejournal.2019.09.006", "category": "环境保护", "unit": "指数", "years": "2004-2013", "year_start": 2004, "year_end": 2013, "city_count": 274, "sample_size": 2740}, {"variable_id": "var_0246", "index": 246, "variable_name": "市委书记年龄", "column_name": "政治精英_AJPS_12648_市委书记年龄", "original_variable_name": "__ajps__市委书记年龄", "source": "AJPS_12648", "category": "政治精英", "unit": "年", "years": "1999-2015", "year_start": 1999, "year_end": 2015, "city_count": 285, "sample_size": 4592}], "missing_variables": [], "common_years": "2004-2013", "agent_note": "该组变量的变量级共同年份为 2004-2013。", "limiting_variable": {"variable_id": "var_0309", "index": 309, "variable_name": "空气污染指数", "column_name": "环境保护_CIE_201909006_空气污染指数", "original_variable_name": "CIE_2019_09_7002927901_空气污染指数", "source": "CIE_10.19581/j.cnki.ciejournal.2019.09.006", "category": "环境保护", "unit": "指数", "years": "2004-2013", "year_start": 2004, "year_end": 2013, "city_count": 274, "sample_size": 2740}, "coverage_method": "基于说明书中的变量级覆盖年份、覆盖城市和样本量；不返回受控数据库观测值。"}