Explanatory variables

Estimated coefficients

p-value

Constant

11.1257

<0.0004

Time trend

0.001389

<0.0004

Time trend²

0.00000058

<0.0004

January

0.069472

<0.0004

February

−0.057158

<0.0004

March

−0.012998

0.160

April

−0.102083

<0.0004

May

−0.122798

<0.0004

June

−0.210181

<0.0004

July

−0.177392

<0.0004

August

−0.173152

<0.0004

September

−0.210230

<0.0004

October

−0.120948

<0.0004

November

−0.089646

<0.0004

ξ/μ

2.32648

<0.0004

(μ² + ξ²)^0.5

0.047928

<0.0004