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	25.4	15.3	13.4	15.0	17.1	12.5	42.6	29.4	25.6	27.3	27.5	36.9	24.0
1981	27.0	28.0	20.7	24.9	17.7	17.3	25.2	17.6	13.7	13.4	12.6	19.8	19.8
1982	12.6	10.6	18.2	15.9	13.1	17.5	13.0	19.9	15.6	18.3	18.2	12.2	15.4
1983	13.7	15.2	18.2	16.8	13.6	25.6	25.9	40.7	37.4	34.5	25.6	28.1	24.6
1984	30.4	25.3	17.9	19.9	22.0	35.9	32.6	34.9	26.3	18.1	13.8	13.3	24.2
1985	19.9	16.0	10.1	9.6	14.2	19.3	20.4	15.8	16.9	12.2	19.5	16.8	15.9
1986	19.4	11.6	10.1	13.4	10.5	9.5	13.9	16.5	11.5	15.5	9.6	8.6	12.5
1987	7.9	8.1	7.2	11.7	32.7	33.9	23.0	10.6	11.8	18.1	17.4	18.3	16.7
1988	18.2	17.0	16.5	17.7	29.2	52.5	55.5	34.4	22.8	21.9	23.9	16.9	27.2
1989	23.3	19.7	20.5	17.1	20.6	23.0	38.2	28.2	15.5	13.1	13.1	8.6	20.1
1990	11.4	8.9	15.2	16.9	20.1	19.8	19.2	16.2	15.2	17.5	21.6	13.9	16.3
1991	17.7	8.9	16.4	20.7	11.6	18.6	30.1	34.5	16.4	20.6	17.2	14.9	19.7
1992	14.5	13.0	12.1	12.4	20.2	22.5	12.8	14.8	13.5	11.2	13.5	8.3	14.1
1993	10.7	7.1	9.2	8.1	9.7	22.0	26.6	21.9	23.1	12.7	22.1	9.8	15.3
1994	18.5	8.7	12.6	19.6	35.0	29.3	23.8	12.6	12.5	11.8	11.4	10.6	17.2
1995	5.2	6.6	1.6	12.4	24.5	21.7	26.2	13.9	22.3	12.1	10.8	16.4	15.2
1996	15.9	13.4	12.7	26.6	18.7	22.7	27.3	18.0	20.3	20.8	12.6	13.0	18.5
1997	17.5	17.9	27.1	15.1	10.1	26.6	29.6	26.4	15.8	21.6	18.1	17.0	21.9
1998	15.1	12.9	11.3	12.3	14.3	28.4	20.7	16.2	13.5	20.3	16.1	11.1	16.0
1999	13.9	16.0	22.5	13.7	12.7	17.6	42.6	34.9	24.9	16.2	17.4	20.0	21.0
2000	20.4	18.1	20.2	18.1	22.9	17.1	11.8	18.2	23.4	12.6	15.8	12.4	17.6
2001	14.7	15.4	17.3	19.6	17.4	22.9	29.9	23.1	19.5	14.5	17.1	11.2	18.5
2002	18.4	15.3	16.0	18.4	11.4	20.9	32.6	26.2	23.0	19.7	14.0	16.7	19.4
2003	20.3	14.9	15.4	17.2	15.0	17.6	17.1	26.0	20.9	25.4	28.9	26.0	20.4
2004	24.0	22.0	30.2	36.3	44.0	35.4	45.1	35.4	21.8	25.5	22.5	16.3	29.9
2005	21.3	28.2	32.0	18.8	21.1	38.6	35.6	26.9	20.7	24.3	21.9	21.6	25.9
2006	22.4	21.3	17.9	14.2	13.3	24.6	16.5	15.1	20.5	20.3	14.3	13.8	17.9
2007	28.2	15.1	14.9	15.7	17.7	28.8	32.8	25.3	20.8	27.0	17.5		22.2
Mean	18.1	15.4	16.7	17.4	19.3	24.4	27.5	23.7	19.5	18.8	17.6	16.0	19.5
High	30.4	28.2	32.0	36.3	44.0	52.5	55.5	43.5	37.4	34.5	28.9	36.9	55.5
Low	5.2	6.6	7.2	8.1	9.7	9.5	11.8	10.6	11.5	11.5	9.6	8.3	5.2