Table 3.

C-statistic and 95% confidence interval.

Year Period	Number of Usable Pairs	Number of Concordant Pairs	Number of Discordant Pairs	C-Statistic (95%CI)
2001–2002	82,566	593,780	258,786	0.70 (0.62–0.77)
2003–2004	324,328	214,520	109,798	0.66 (0.55–0.77)
2005–2006	141,552	105,692	35,860	0.75 (0.59–0.88)
2007–2008	88,635	60,128	28,507	0.68 (0.48–0.85)
2001–2010	4,934,832	3,659,189	1,275,643	0.74 (0.69–0.79)

CI = confidence interval.