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Table 8 Mean values of the covariates before and after the matching (caliper matching)

From: The effects of compulsory health insurance on birth outcomes: evidence from China’s UEBMI scheme

   Mean    t-test
Variable Sample Treated Control %bias %|bias| reduction t p > |t|
Age Unmatched 30.76 30.78 −0.40   − 0.76 0.45
  Matched 30.76 30.74 0.60 −47.50 1.39 0.17
Age square Unmatched 959.80 965.90 −2.40   −4.70 <0.001
  Matched 959.80 958.30 0.60 74.50 1.48 0.14
Migrant Unmatched 0.33 0.49 −31.40   −61.24 <0.001
  Matched 0.33 0.34 −0.80 97.60 −1.77 0.08
Gravidity Unmatched 1.73 1.97 −21.20   −41.98 <0.001
  Matched 1.73 1.73 0.50 97.40 1.37 0.17
Parity Unmatched 1.22 1.32 −19.90   −39.27 <0.001
  Matched 1.22 1.22 0.30 98.40 0.78 0.43
Employed Unmatched 0.98 0.89 35.70   75.45 <0.001
  Matched 0.98 0.98 0.01 100.00 −0.06 0.95
Ethnic status Unmatched 0.99 0.99 1.10   2.05 0.04
  Matched 0.99 0.99 −1.20 −17.20 −2.93 <0.001
Nationality Unmatched 1.00 0.99 10.70   23.92 <0.001
  Matched 1.00 1.00 0.01 99.70 0.58 0.56
Marriage status Unmatched 1.00 1.00 5.90   12.33 <0.001
  Matched 1.00 1.00 −0.40 92.70 −1.62 0.11
High-risk pregnancy Unmatched 0.55 0.60 −11.00   −21.30 <0.001
  Matched 0.55 0.55 −0.40 96.70 −0.80 0.42
Pregnancy complications Unmatched 0.14 0.16 −7.90   −15.52 <0.001
  Matched 0.14 0.13 0.40 94.90 0.95 0.34
Any condition (gestational diabetes, hypertension, anemia) Unmatched 0.09 0.13 −12.60   −24.80 <0.001
Matched 0.09 0.09 0.80 93.70 1.94 0.05