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	29.8	15.8	20.5	34.5	31.4	21.0	30.9	12.8	16.0	20.2	21.8	34.7	24.1
1981	36.1	26.7	18.7	19.6	16.0	17.4	18.9	18.6	12.8	13.0	13.6	26.7	19.8
1982	18.9	14.6	18.6	17.5	14.3	16.1	18.1	18.0	17.8	20.8	17.8	13.8	17.2
1983	17.0	25.2	19.7	16.1	14.5	13.5	19.7	32.1	19.1	15.4	15.3	11.5	18.3
1984	17.9	14.4	20.0	18.5	20.3	11.6	11.9	19.2	16.7	10.1	10.1	11.5	15.2
1985	11.6	13.3	13.0	17.6	10.1	10.7	13.7	22.6	19.3	17.0	17.1	13.7	15.0
1986	21.5	19.9	19.6	38.7	39.0	18.5	23.1	18.6	18.7	25.1	22.0	12.2	23.1
1987	16.2	23.5	15.3	18.7	31.5	24.3	19.4	15.6	15.4	19.7	19.4	14.5	19.4
1988	20.1	14.6	16.4	14.9	26.7	62.5	48.1	20.1	19.0	18.7	15.8	13.4	24.2
1989	15.5	11.7	19.4	24.3	12.5	19.2	18.3	9.9	15.4	10.1	8.1	10.1	14.3
1990	9.0	11.4	12.2	15.5	13.9	13.7	14.7	21.7	19.4	19.6	24.8	12.7	15.9
1991	17.5	16.7	21.2	18.8	14.0	24.5	26.5	33.9	11.6	17.5	21.4	20.5	20.3
1992	16.6	30.0	17.9	21.3	25.0	18.7	18.4	17.7	15.6	16.9	14.8	13.5	18.9
1993	17.9	18.1	20.4	19.5	14.6	16.6	28.2	18.5	11.6	17.8	21.0	11.0	17.9
1994	19.6	15.5	14.7	21.6	24.3	20.5	16.8	15.4	21.8	18.5	16.7	14.9	18.3
1995	17.9	17.2	19.9	16.1	21.9	29.1	31.8	29.6	18.3	18.1	18.5	13.8	21.0
1996	26.4	21.2	20.0	50.0	32.8	32.3	28.0	19.9	21.9	20.9	27.0	19.0	26.69
1997	18.6	20.3	21.3	37.3	26.4	21.6	22.1	18.4	14.5	20.9	17.3	17.6	21.3
1998	22.8	18.5	18.4	16.9	20.3	28.9	17.5	22.1	22.3	28.9	19.4	17.8	21.2
1999	22.7	20.7	33.4	23.8	20.9	19.9	27.2	24.7	26.7	18.8	230	18.7	23.4
2000	16.9	23.0	24.6	19.0	22.7	26.6	16.8	22.4	21.7	19.2	18.9	18.4	20.8
2001	18.6	18.5	24.9	21.2	21.6	22.0	26.8	19.8	23.2	21.1	15.9	19.8	22.0
2002	20.4	15.6	22.0	16.6	22.2	27.7	24.4	22.6	41.1	41.7	28.8	25.6	25.8
2003	27.9	23.8	23.6	24.5	37.4	30.0	27.2	23.8	22.9	34.6	40.1	28.0	26.8
2004	27.2	28.9	37.1	30.1	34.2	22.3	24.4	27.2	29.2	21.0	22.1	19.6	26.9
2005	21.3	32.8	30.1	21.4	33.2	25.0	28.4	20.0	20.3	18.01	13.33	21.0	23.7
2006	22.4	25.4	26.1	21.7	32.9	27.8	43.2	29.3	33.4	45.8	26.0	29.9	30.4
2007	38.0	25.2	21.3	37.5	32.3	40.0	30.4	26.4	38.6	38.2	30.1		32.5
Mean	20.9	20.1	21.1	23.2	23.8	23.6	24.1	21.5	20.9	21.7	20.4	17.9	21.6
High	38.0	32.8	37.1	50.0	39.0	62.5	48.1	33.9	41.4	45.8	40.1	34.7	62.5
Low	9.0	11.4	12.2	14.9	10.1	10.7	11.9	9.9	11.6	10.1	8.1	10.1	8.1