Table 3. Results of Wooldridge model.

		OLS	Ridge	Residualization
Intercept	${\widehat{\mathrm{\text{β}}}}_1$	0.050 **	0.058	0.183 **
	(s.d.)	(0.008)	n/a	(0.007)
${\mathbf{c}}_{13}$	${\widehat{\mathrm{\text{β}}}}_2$	−0.557 **	−0.464	1.067 **
	(s.d.)	(0.065)	n/a	(0.008)
${\mathbf{c}}_{26}$	${\widehat{\mathrm{\text{β}}}}_3$	1.562 **	1.473
	(s.d.)	(0.063)	n/a
${\mathbf{e}}_{{\mathbf{c}}_{26}}$	${\widehat{\mathrm{\text{β}}}}_{3_0}$			1.562 **
	(s.d.)			(0.063)
$R^2$		0.9935	n/a	0.9935
F statistic		9794	n/a	9794
p-value (of F)		$<2.2\cdot {10}^{-16}$	n/a	$<2.2\cdot {10}^{-16}$

**, * mean the coefficient is statistically significant at 0.01 (99% level of confidence) and at 0.05 (95% level of confidence), respectively.