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	26.0	24.6	25.0	27.6	32.0	27.2	33.9	28.5	23.9	25.7	27.2	32.0	27.8
1981	19.3	26.0	22.5	27.4	22.2	23.0	23.3	26.9	17.9	17.1	27.8	26.1	23.3
1982	23.6	24.5	23.2	25.0	22.2	26.1	24.5	32.6	25.5	33.5	27.1	18.5	25.5
1983	14.1	25.4	25.1	27.2	23.9	22.5	34.9	44.6	32.7	20.3	18.2	13.5	25.2
1984	20.8	23.5	13.5	22.9	10.6	22.7	14.1	13.4	12.2	9.4	8.5	9.9	15.1
1985	12.9	12.0	9.3	9.6	12.9	14.8	15.4	31.5	19.8	19.3	18.5	12.4	15.7
1986	24.7	15.6	18.1	48.3	47.6	50.5	25.7	22.8	23.2	15.9	23.4	26.5	28.5
1987	19.4	28.5	30.0	22.9	39.5	49.5	34.5	31.5	20.9	20.5	38.0	19.4	29.5
1988	13.9	12.2	29.6	25.0	31.7	54.0	58.7	34.8	27.8	26.7	37.0	21.6	31.1
1989	32.7	30.4	27.6	39.1	32.2	40.1	53.4	28.0	19.6	16.8	14.7	12.2	28.9
1990	17.8	19.7	20.2	16.8	33.3	26.7	34.6	40.4	33.2	24.5	34.3	21.0	26.9
1991	25.2	19.6	31.7	29.0	19.7	35.8	39.8	50.2	17.8	18.2	18.8	17.3	26.9
1992	17.6	43.5	33.4	27.4	37.0	38.2	21.5	38.3	18.7	19.7	24.7	14.3	27.9
1993	13.9	15.4	14.5	36.8	26.1	24.7	27.9	23.0	16.5	15.9	30.8	17.9	22.0
1994	23.0	13.5	21.8	19.5	39.4	57.3	21.4	25.4	21.0	18.6	21.3	20.6	25.2
1995	15.4	12.2	18.8	16.7	17.9	49.0	29.5	26.9	24.6	18.6	18.5	20.7	22.5
1996	37.8	32.1	15.8	54.3	43.8	46.9	37.7	42.5	33.3	35.4	20.0	13.1	34.4
1997	25.5	43.6	18.7	32.7	25.6	33.5	30.4	28.0	14.0	20.0	15.4	16.1	25.3
1998	17.2	12.3	21.8	42.6	26.0	42.3	24.4	30.2	18.7	23.1	12.6	14.5	23.8
1999	22.6	22.0	33.1	43.5	28.7	22.8	39.0	19.7	12.0	13.8	15.1	12.5	23.7
2000	14.9	13.9	18.5	16.3	22.2	28.1	16.7	15.9	16.0	14.8	15.1	12.8	18.8
2001	22..6	13.1	24.4	17.5	18.2	20.7	71.0	35.7	36.3	38.8	35.2	32.3	30.5
2002	32.2	25.0	24.1	66.7	46.7	45.4	47.7	27.0	27.2	41.1	37.1	17.8	36.5
2003	25.9	38.7	43.5	38.3	36.0	41.9	47.1	34.5	35.8	30.7	29.7	22.2	34.5
2004	31.6	21.0	39.0	37.4	37.0	31.7	27.0	29.9	49.6	22.1	35.3	20.8	31.9
2005	23.1	18.9	58.6	22.4	24.0	30.4	32.9	26.6	27.1	26.7	20.5	43.2	29.5
2006	26.5	35.4	17.7	20.6	31.1	26.6	54.5	19.4	24.1	37.2	32.8	24.0	29.2
2007	31.8	27.2	32.7	25.3	26.5	33.4	47.7	22.8	40.0	23.4	17.9		29.9
Mean	22.6	23.2	25.2	30.0	29.1	34.5	34.6	30.0	24.6	23.1	24.1	19.7	26.7
High	37.8	43.6	58.6	66.7	47.6	57.3	71.0	50.2	49.6	41.1	38.0	43.2	71.0
Low	12.9	12.0	9.3	9.6	10.6	14.8	14.1	13.4	12.0	9.4	8.5	9.9	8.5