Table 2. Summary of all Pearson’s correlation coefficients for the US.

Time interval	ρ	95% CI	p-value	Signif
1997–2008 vs 2010–2015	−0.5208	(−0.88, 0.219)	0.1506
1998–2008 vs 2010–2015	−0.5001	(−0.874, 0.246)	0.1704
1999–2008 vs 2010–2015	−0.5814	(−0.899, 0.135)	0.1006
2000–2008 vs 2010–2015	−0.6186	(−0.909, 0.077)	0.0757
2001–2008 vs 2010–2015	−0.6289	(−0.912, 0.061)	0.0696
2002–2008 vs 2010–2015	−0.7027	(−0.932, −0.072)	0.0347	*
2003–2008 vs 2010–2015	−0.7517	(−0.944, −0.175)	0.0195	*
2004–2008 vs 2010–2015	−0.7024	(−0.932, −0.072)	0.0349	*
2005–2008 vs 2010–2015	−0.7489	(−0.944, −0.169)	0.0202	*
2006–2008 vs 2010–2015	−0.6112	(−0.907, 0.089)	0.0804
2007–2008 vs 2010–2015	−0.6498	(−0.918, 0.025)	0.0582

ρ stands for correlation coefficient.