Dep. Variable: gfr R-squared: 0.314 Model: OLS Adj. R-squared: 0.294 Method: Least Squares F-statistic: 15.80 Date: Sat, 18 Mar 2023 Prob (F-statistic): 2.24e-06 coef std err t P>|t] [0.025 0.975] Intercept 107.0563 6.050 17.696 0.000 94.988 119.125 0.0717 0.382 0. 187 0.852 -0.691 0.835 tsq -0.0080 0.005 -1.568 0.122 -0.018 0.002 Gfr is the fertility rate. T is a trend variable; tsq is the trend variable squared