Jun

Feb

Mar

Apr

May

June

July

Aug

Sep

Oct

Nov

Dec

1970-1979

−4.6

−20.9

−22.3

−21.9

−35.6

−50.3

−57.0

−52.7

−37.1

−17.4

−10.1

−7.6

1980-1989

−4.1

−2.6

−21.8

−32.6

−34.8

−50.7

−58.7

−52.5

−37.6

−28.2

−6.2

−7.4

1990-1999

−9.1

−4.4

−7.8

−28.3

−42.5

−46.9

−56.3

−45.5

−42.7

−21.2

−24.7

−6.7

2000-2016

−15.1

−14.7

−11.9

−22.7

−34.3

−34.5

−50.7

−49.8

−42.7

−28.8

−26.2

−12.1

N = Average (D)

−8.2

−10.5

−16.0

−26.4

−36.8

−45.6

−55.7

−50.1

−40.2

−23.9

−16.8

−8.5