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	24.2	8.2	13.0	15.5	14.8	6.3	24.8	21.7	15.0	17.4	17.5	24.5	16.9
1981	16.2	16.7	12.2	13.2	16.8	15.2	22.3	21.1	15.0	13.8	10.6	21.2	16.2
1982	10.3	8.0	10.0	9.1	8.0	9.5	9.8	21.7	18.4	18.6	20.6	12.2	13.2
1983	12.8	16.8	17.2	15.1	16.4	9.6	19.1	28.3	25.2	20.0	15.1	14.5	17.5
1984	17.6	14.4	8.6	15.5	9.4	10.2	19.6	21.1	13.3	10.3	9.3	11.2	13.4
1985	7.0	7.7	6.8	6.0	5.6	8.8	14.5	14.6	18.9	17.9	13.2	7.0	10.7
1986	11.3	11.3	11.7	15.9	17.7	17.3	26.5	18.5	21.2	25.3	14.1	13.6	17.0
1987	20.8	23.7	17.0	18.7	30.5	35.9	23.8	24.4	19.4	21.1	12.1	14.3	21.8
1988	15.6	15.9	11.7	9.7	26.6	56.0	54.8	35.7	18.6	20.2	19.9	13.5	24.8
1989	22.3	13.6	17.1	16.8	13.3	23.0	33.1	12.7	17.5	17.9	12.3	6.1	18.1
1990	8.1	7.5	10.6	10.1	14.9	18.8	19.0	19.0	19.3	17.2	19.7	10.6	14.7
1991	10.8	8.8	14.5	13.7	13.2	21.4	321	32.1	12.2	14.2	12.9	11.2	16.4
1992	11.0	17.1	9.4	13.9	19.8	22.2	15.3	17.9	15.7	11.7	17.5	6.7	14.8
1993	9.1	5.7	8.2	13.5	13.5	14.6	24.4	14.9	16.8	17.3	19.9	9.6	13.9
1994	16.4	13.6	17.5	18.0	27.1	33.4	22.7	10.8	12.1	12.1	8.7	11.1	17.1
1995	7.9	7.5	7.8	9.9	15.3	24.6	17.4	12.7	17.3	12.6	13.7	12.0	13.2
1996	20.5	14.5	14.8	36.0	26.2	39.4	33.5	23.6	19.1	15.4	15.0	12.2	22.5
1997	13.4	15.7	23..6	21.0	19.6	17.8	32.6	33.9	16.9	25.1	20.5	15.1	21.3
1998	21.9	11.6	19.9	17.9	21.4	31.3	25.2	18.5	18.9	22.2	14.8	11.4	19.6
1999	16.4	16.8	20.5	17.3	17.9	19.1	39.9	30.4	16.0	13.4	14.9	13.9	19.7
2000	22.4	14.4	25.6	16.8	26..0	28.8	20.4	16.2	18.5	17.4	17.0	15.7	19.9
2001	17.9	12.1	19.2	20.8	21.3	16.6	41.6	19.1	17.3	15.0	21.4	11.2	19.4
2002	12.0	13.1	11.6	11.4	23.2	20.2	42.1	24.7	28.0	19.2	16.7	13.0	19.6
2003	20.2	11.4	18.5	12.5	22.6	19.7	16.6	25.4	22.8	28.6	25.2	18.3	20.1
2004	26.0	17.9	23.6	26.3	27.6	29.9	20.4	23.4	15.1	18.0	15.5	16.7	21.7
2005	20.1	20.9	22.6	20.1	25.0	33.8	42.2	22.4	16.0	10.45	9.51	19.5	21.9
2006	19.1	23.1	30.7	19.8	31.3	28.8	26.7	30.2	39.5	43.5	26.9	26.3	28.8
2007	38.1	27.9	23.0	36.8	42.0	38.1	30.1	27.3	39.2	31.4	22.6		32.4
Mean	16.8	14.1	16.0	16.8	20.4	23.2	26.8	22.7	19.4	18.8	16.1	13.8	18.8
High	38.1	27.9	30.7	36.8	42.0	56.0	54.8	35.7	39.5	43.5	26.9	26.3	56.0
Low	7.0	5.7	6.8	6.0	5.6	6.3	9.8	10.8	12.1	10.3	8.7	6.1	5.6