Volatility is measurement of the change in price over a given period. It is often expressed as a percentage and computed as the annualized standard deviation of the percentage change in daily price.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Yearly Average
1980	22.5	16.5	14.8	21.3	22.0	18.8	34.4	25.3	23.0	29.2	27.6	35.0	24.2
1981	19.8	24.2	19.8	16.9	12.5	16.0	29.0	20.5	16.6	20.3	11.9	16.4	18.7
1982	12.7	14.7	16.6	17.4	19.3	18.4	11.1	23.7	18.8	17.7	17.6	9.6	16.5
1983	13.2	18.8	20.4	16.7	13.0	28.0	26.3	42.5	39.2	32.9	27.6	28.7	25.6
1984	33.8	34.0	22.3	25.2	25.7	40.7	38.0	31.9	29.9	23.8	24.9	17.4	29.0
1985	27.3	25.4	23.3	25.7	25.7	20.1	20.1	26.8	16.4	21.1	25.2	29.9	23.9
1986	20.4	17.9	31.6	30.7	23.3	15.4	23.1	22.6	18.4	40.2	19.8	17.1	23.4
1987	18.1	17.6	16.9	18.8	32.1	28.5	24.2	20.7	11.5	21.4	17.0	21.5	20.7
1988	28.8	20.9	19.1	23.0	22.8	42.8	51.3	36.4	25.4	21.9	23.2	22.1	28.1
1989	25.9	18.6	13.6	15.6	21.9	25.1	30.1	27.7	16.9	16.3	17.1	9.7	19.9
1990	16.1	15.6	20.8	19.4	21.6	23.4	22.7	18.3	15.2	12.8	20.8	9.2	18.2
1991	23.1	14.1	21.9	21.0	18.8	18.6	36.4	34.9	18.4	21.9	14.3	18.9	22.0
1992	14.1	14.5	19.8	12.3	17.7	24.3	15.1	14.2	23.2	16.6	20.5	15.0	17.3
1993	21.0	14.1	14.0	13.0	11.6	25.8	23.4	19.8	24.1	12.9	26.8	17.2	18.6
1994	22.6	14.0	15.4	21.5	31.3	25.6	24.2	14.3	16.8	20.7	20.7	22.1	20.8
1995	16.2	14.5	21.7	15.2	29.4	25.5	26.1	11.7	18.4	11.4	9.2	13.5	17.7
1996	15.2	10.9	10.7	16.4	16.1	18.7	25.1	17.6	15.9	19.9	13.5	10.6	15.9
1997	17.8	11.6	26.6	12.3	18.0	14.4	23.0	22.4	16.8	15.8	19.5	16.1	17.9
1998	17.4	16.7	13.8	18.8	18.2	21.5	15.4	15.1	19.4	14.0	16.4	11.2	16.5
1999	13.8	24.9	30.2	25.8	20.1	14.4	32.4	36.1	228	14.5	18.5	20.0	22.8
2000	24.2	19.3	28.3	21.1	22.1	18.6	12.0	15.9	20.7	6.6	19.3	15.5	18.6
2001	10.6	22.6	16.0	16.9	14.6	22.9	38.8	25.9	21.0	21.0	20.6	16.0	20.6
2002	21.2	20.2	23.9	20.1	18.8	19.4	27.2	22.2	14.8	23.0	21.5	19.3	21.0
2003	17.9	17.2	19.6	15.9	21.0	18.9	10.2	18.8	24.6	27.3	29.8	19.9	18.2
2004	26.7	23.4	35.2	34.9	36.5	28.6	27.2	30.8	26.7	33.4	29.1	16.5	29.1
2005	16.7	40.7	29.0	17.4	22.2	39.2	28.5	25.8	30.0	22.1	19.3	19.1	25.8
2006	20.0	25.0	17.9	18.8	24.1	21.3	20.2	20.7	12.8	22.2	13.0	15.9	19.3
2007	24.4	17.2	15.9	25.7	17.1	22.3	15.8	23.7	16.6	19.1	18.5		19.7
Mean	20.1	19.5	20.7	19.9	21.4	23.5	25.4	23.8	20.5	20.8	20.1	17.9	21.1
High	33.8	40.7	35.2	34.9	36.5	42.8	51.3	42.5	39.2	40.2	29.8	35.0	51.3
Low	10.6	10.9	10.7	12.3	11.6	14.4	10.2	11.7	11.5	6.6	9.2	9.2	6.6