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	30.5	11.9	9.5	14.9	16.7	9.2	43.0	25.7	26.2	28.2	30.2	41.5	24.0
1981	30.6	27.5	17.9	23.5	18.5	15.0	20.5	19.0	14.2	8.0	12.8	18.8	18.9
1982	14.5	9.4	15.1	15.8	8.9	15.3	12.0	18.4	11.1	17.6	18.3	15.2	14.3
1983	15.5	13.8	19.6	14.1	13.6	24.7	28.7	47.4	44.3	34.0	25.9	31.2	26.1
1984	33.0	20.7	14.5	22.5	23.8	25.3	27.0	28.0	21.5	19.9	12.3	19.5	22.3
1985	16.1	19.1	20.1	12.9	15.6	19.5	31.2	14.6	20.5	17.0	23.0	24.5	19.5
1986	22.8	15.9	14.4	15.0	13.0	9.1	10.7	16.7	10.4	11.7	6.3	9.7	13.0
1987	12.0	10.7	12.4	15.3	38.2	38.8	220	11.8	22.2	23.5	25.7	23.5	21.3
1988	22.6	22.8	16.2	14.1	30.9	55.2	29.5	34.1	25.8	25.6	27.6	19.2	29.4
1989	26.4	21.0	23.4	16.4	17.9	25.7	34.6	21.0	15.0	13.8	11.9	10.3	19.8
1990	9.3	8.8	18.8	23.3	19.3	17.5	24.5	16.5	19.7	23.6	20.5	18.4	18.3
1991	19.2	13.1	18.7	23.2	8.2	20.9	30.3	42.4	18.2	18.9	15.2	15.8	20.4
1992	14.9	12.0	10.8	10.5	21.7	17.7	9.8	12.6	10.5	8.0	13.3	9.0	12.6
1993	6.9	7.0	7.9	7.6	8.8	20.3	26.9	17.4	18.4	12.2	22.5	9.9	13.8
1994	11.8	9.3	12.8	18.3	34.0	27.8	17.7	11.5	10.7	11.5	8.1	17.1	15.8
1995	10.9	10.1	13.8	16.1	16.1	20.2	26.0	14.3	24.7	12.7	12.7	18.7	17.2
1996	17.7	16.1	18.1	27.9	18.9	21.8	22.0	13.4	20.4	21.7	17.1	16.3	19.3
1997	18.5	22.0	28.4	29.0	21.7	26.4	27.5	24.0	25.7	27.1	30.4	19.0	25.0
1998	19.3	13.1	18.8	21.7	20.9	41.4	30.1	16.1	18.7	34.4	24.9	17.0	23.0
1999	17.0	22.6	22.2	18.0	17.1	19.9	42.9	36.4	28.8	21.7	22.2	17.2	23.8
2000	21.2	24.2	20.0	19.6	23.3	16.9	14.4	15.2	21.3	19.5	26.1	12.0	19.4
2001	16.1	17.3	21.8	21.5	23.0	21.9	24.6	20.0	24.9	17.5	17.1	15.5	20.1
2002	30.6	18.6	16.2	17.3	17.2	20.6	32.6	25.3	21.0	18.8	13.9	16.6	20.7
2003	23.0	20.2	19.1	24.4	18.5	21.2	18.7	30.2	21.3	24.7	24.4	32.8	23.2
2004	28.0	28.3	25.9	36.1	49.9	36.7	37.9	38.7	15.7	25.7	25.5	23.2	31.0
2005	30.3	33.2	33.3	20.8	23.7	36.5	33.1	25.1	14.7	24.2	24.8	29.2	27.4
2006	23.6	22.3	17.2	18.1	13.3	28.2	13.2	14.3	21.3	21.6	16.8	16.5	18.9
2007	33.8	15.7	20.3	15.3	22.5	32.1	43.3	25.7	23.2	33.2	20.4		26.0
Mean	20.6	17.3	18.1	19.0	20.9	24.5	27.3	22.7	20.3	20.6	19.6	19.2	20.8
High	33.8	33.2	33.3	36.1	49.9	55.2	59.5	47.4	44.3	34.4	30.4	41.5	59.5
Low	6.9	7.0	7.9	7.6	8.4	9.1	9.8	11.5	10.4	8.0	6.3	9.0	6.3