Year,Jan.,Feb.,Mar.,Apr.,May,Jun.,Jul.,Aug.,Sept.,Oct.,Nov.,Dec.,Mean
1965,26.48,28.59,30.01,28.89,27.86,26.85,25.45,24.65,24.25,24.44,25.20,26.17,26.57
1966,27.95,28.90,28.45,27.55,25.68,24.21,23.37,22.14,22.20,23.00,23.53,24.95,25.16
1967,26.76,28.02,29.62,28.50,27.24,24.78,22.85,22.22,21.50,22.24,23.47,23.71,25.08
1968,26.58,27.90,28.30,27.08,25.24,23.91,23.39,24.21,24.13,24.35,24.60,26.10,25.48
1969,27.27,28.89,29.87,29.45,28.67,27.41,24.69,24.17,24.14,25.68,26.16,26.88,26.94
1970,27.73,28.73,29.01,27.90,26.37,24.11,21.76,21.67,22.24,22.97,24.16,24.99,25.14
1971,26.85,27.89,28.13,29.29,26.07,24.56,23.76,22.31,22.72,24.02,24.90,25.10,25.47
1972,26.89,28.93,30.05,29.12,27.85,26.99,26.76,26.59,25.70,25.96,26.82,27.62,27.44
1973,28.47,30.05,29.95,27.47,26.48,24.46,23.26,22.61,22.68,22.89,24.22,25.41,25.66
1974,26.92,29.29,28.95,29.70,27.72,25.58,24.09,23.52,23.38,23.04,23.71,24.08,25.83
1975,26.53,27.43,29.14,28.61,26.19,24.67,23.59,22.43,22.06,22.07,22.42,24.00,24.93
1976,27.06,28.92,30.06,29.74,28.35,27.29,26.46,25.95,24.89,25.37,25.89,26.72,27.22
1977,28.59,30.00,30.11,29.00,27.30,26.11,24.22,22.28,22.17,23.10,24.51,25.41,26.07
1978,26.67,28.00,27.57,27.26,25.91,23.18,22.89,21.74,21.56,22.55,23.90,25.12,24.70
1979,27.38,27.86,28.89,28.40,26.70,25.07,24.25,23.30,23.86,23.88,24.79,25.11,25.79
1980,27.06,28.26,29.14,28.92,26.82,25.17,23.87,22.77,22.33,23.00,23.97,24.90,25.52
1981,25.98,27.74,28.33,27.70,26.65,24.91,23.21,22.51,21.97,22.70,23.57,25.43,25.06
1982,26.64,28.23,27.97,27.19,26.45,25.10,24.37,24.07,24.87,25.78,27.21,27.68,26.30
1983,29.40,30.12,30.11,29.79,28.79,28.34,27.64,26.25,24.68,24.66,24.70,25.61,27.51
1984,26.63,27.36,28.76,27.10,25.61,23.88,22.66,22.21,22.42,22.74,24.25,25.34,24.91
1985,26.03,26.70,27.75,27.50,24.52,24.22,22.43,21.37,21.51,22.20,23.84,24.63,24.39
1986,26.94,28.59,29.24,27.63,26.43,24.53,23.88,23.41,23.24,23.80,24.64,25.84,25.68
1987,27.59,28.61,29.27,29.36,27.70,25.96,24.87,24.39,24.74,25.10,25.62,26.25,26.62
1988,27.43,28.30,28.37,26.26,25.49,23.22,21.64,20.96,21.65,22.01,22.92,24.61,24.40
1989,26.53,28.89,28.51,28.77,26.35,24.38,23.26,22.90,22.09,23.07,23.96,24.59,25.27
1990,26.65,28.38,29.14,28.49,26.95,24.92,23.36,22.71,22.96,22.60,23.47,25.02,25.39
1991,26.69,28.46,28.87,27.22,27.48,25.76,24.44,23.70,23.22,23.85,24.57,26.09,25.86
1992,26.93,29.03,29.86,29.01,27.93,25.38,23.73,22.59,22.31,22.87,23.79,25.37,25.73
1993,26.93,28.48,29.02,29.22,27.85,26.32,24.80,24.05,24.06,23.91,24.79,26.01,26.29
1994,27.63,28.70,27.97,25.99,26.01,24.57,24.00,22.21,22.33,23.96,24.83,26.02,25.35
1995,28.03,29.35,29.20,26.07,25.89,25.00,23.38,22.24,22.57,22.99,23.72,24.74,25.27
1996,26.60,28.36,28.70,26.47,25.33,23.79,22.55,21.85,21.40,22.57,23.01,23.54,24.51
1997,26.18,28.29,29.04,28.77,28.13,27.82,27.50,27.19,27.24,26.98,27.62,28.64,27.78
1998,30.27,30.32,30.31,29.40,28.60,27.47,25.42,24.37,23.92,23.96,24.57,25.30,26.99
,,,,,,,,,,,,,
Mean,27.18,28.58,29.05,28.20,26.84,25.29,24.05,23.28,23.15,23.66,24.51,25.50,
,,,,,,,,,,,,,
Median,26.92,28.53,29.03,28.50,26.68,24.96,23.81,22.74,22.70,23.08,24.38,25.35,
,,,,,,,,,,,,,
Standard Deviation,0.92,0.80,0.76,1.12,1.10,1.34,1.44,1.52,1.37,1.25,1.18,1.11,
,,,,,,,,,,,,,
Coefficient of Variation,3.39,2.80,2.61,3.98,4.11,5.31,6.00,6.54,5.93,5.27,4.80,4.36,