| Year | Area | Sample | Mean | S.D. | SEM | t | p |
|---|---|---|---|---|---|---|---|
| 2011 | Urban | 4022 | 0.460 | 0.498 | 0.008 | −4.718 | 0.000 |
| Rural | 4594 | 0.510 | 0.500 | 0.007 | |||
| 2014 | Urban | 2684 | 0.350 | 0.476 | 0.009 | −1.745 | 0.081 |
| Rural | 3237 | 0.370 | 0.483 | 0.008 | |||
| 2018 | Urban | 7321 | 0.300 | 0.459 | 0.005 | −5.481 | 0.000 |
| Rural | 6054 | 0.340 | 0.475 | 0.006 |