Year,Value,Contiguous U.S. (Lower 48),Wind,Apr,(mph)
1940,8.098
1941,7.392
1942,8.032
1943,8.118
1944,8.042
1945,8.453
1946,7.661
1947,8.181
1948,8.667
1949,7.545
1950,8.68
1951,8.387
1952,7.558
1953,8.556
1954,8.249
1955,8.655
1956,8.191
1957,8.164
1958,8.114
1959,8.164
1960,8.711
1961,8.878
1962,7.95
1963,8.653
1964,8.903
1965,7.875
1966,7.98
1967,8.902
1968,8.369
1969,8.131
1970,8.687
1971,8.252
1972,8.321
1973,8.51
1974,8.904
1975,8.485
1976,8.088
1977,7.548
1978,8.585
1979,7.853
1980,7.821
1981,8.357
1982,8.585
1983,8.14
1984,8.781
1985,7.873
1986,8.333
1987,7.494
1988,7.821
1989,7.594
1990,7.696
1991,8.14
1992,7.442
1993,8.083
1994,8.201
1995,8.028
1996,8.763
1997,8.039
1998,7.655
1999,8.494
2000,8.091
2001,8.298
2002,8.132
2003,8.233
2004,7.91
2005,8.326
2006,8.222
2007,8.059
2008,8.415
2009,8.675
2010,8.515
2011,9.098
2012,8.169
2013,8.44
2014,8.767
2015,7.993
2016,8.074
2017,8.292
2018,8.475
2019,8.126
2020,7.986
2021,7.984
2022,9.358
2023,8.238
2024,8.588
2025,8.21