Year,Jan.,Feb.,Mar.,Apr.,May,Jun.,Jul.,Aug.,Sept.,Oct.,Nov.,Dec.,Mean
1987,,,,,,24.32,23.70,22.84,23.96,24.21,24.02,25.10,24.02
1988,26.57,28.65,30.03,29.57,26.94,24.32,21.49,20.54,20.92,21.38,22.13,23.86,24.70
1989,26.93,29.40,31.05,29.39,25.92,24.05,23.21,22.69,21.43,22.21,23.23,23.87,25.28
1990,25.71,27.77,29.57,29.62,26.71,25.03,23.33,21.98,22.41,21.63,22.12,24.01,24.99
1991,26.36,28.21,28.81,28.80,27.23,24.73,23.22,22.71,22.00,22.61,23.62,24.60,25.24
1992,25.87,27.95,29.56,28.23,27.78,25.56,23.17,21.83,21.39,21.98,22.87,24.96,25.09
1993,27.03,27.80,29.50,29.53,26.73,25.33,23.42,23.15,23.55,22.79,23.41,24.61,25.57
1994,26.87,28.36,30.33,29.18,26.45,23.99,23.17,21.04,21.38,23.19,24.03,24.62,25.22
1995,26.53,29.52,30.21,27.83,26.43,24.74,22.19,20.86,20.89,21.50,22.93,23.85,24.79
1996,26.13,28.12,28.88,28.06,26.60,22.93,21.63,20.85,20.19,22.08,22.09,23.01,24.21
1997,25.93,27.90,28.28,28.66,27.20,27.35,26.02,25.95,26.11,25.25,26.00,27.25,26.82
1998,29.17,29.32,29.79,28.75,27.85,26.60,24.90,24.34,23.59,23.80,24.45,25.18,26.48
,,,,,,,,,,,,,
Mean,26.64,28.45,29.64,28.87,26.89,24.91,23.29,22.40,22.32,22.72,23.41,24.58,
,,,,,,,,,,,,,
Median,26.53,28.21,29.57,28.80,26.73,24.73,23.22,22.34,21.71,22.41,23.32,24.60,
,,,,,,,,,,,,,
Standard Deviation,0.95,0.67,0.78,0.64,0.58,1.19,1.26,1.59,1.69,1.20,1.13,1.05,
,,,,,,,,,,,,,
Coefficient of Variation,3.57,2.34,2.63,2.21,2.17,4.79,5.41,7.11,7.56,5.26,4.85,4.29,