The quality and representativeness of the data

We used Myer’s index to test the data quality, using age as the basis of the logic judgment process [28]. Myer’s index should not be bigger than 60; otherwise the quality of the data was poor for us to analyze [29]. We used goodness for fit test to observe the fitting degree of the distribution of sample data and the distribution of theoretical frequency. If the test results showing no statistical significance (P values > 0.05), the representativeness of the data cannot be regarded as poor.

The results of the Myer’s index of this study from 2003/2004 to 2014 were 4.00, 5.12, 12.02, 8.52, 3.54, and 7.07, respectively. Correspondingly, the value of χ² of the test of goodness for fit of sex were 0.0014, 0.0002, 0.0005, 0.1103, 0.0021, 0.5396, P values > 0.05. Therefore, the quality and representativeness of the data cannot be regarded as poor.