Year

Regression model

R²

P value

2004

Y = 98 + 0.196x

0.85

0.0079

2005

Y = 82 + 0.390x

0.97

0.0004

2006

Y = 88 + 0.554x

0.94

0.0012

3-year average

Y = 95 + 0.115x + 0.002x²

0.99

0.0005

2004-2006

Y = −2.95 + 0.179x

0.92

0.0029