Equation

Intercept

Per capita personal income (t-statistic)

Per capita personal income squared (t-statistic)

Number of counties (t-statistic)

Adjusted R² (F-statistic)

(1)

−3.206 (−14.597)^*

1.698 (15.366)^*

0.110 (236.125)^*

(2)

113.238 (2.546)^*

−115.482 (−2.580)^*

29.479 (2.618)^*

0.113 (121.853)^*

(3)

113.644 (2.822)^*

−117.928 (−2.859)^*

30.094 (2.901)^*

0.000455 (18.410)^*

0.247 (208.682)^*