Year

Number of Attacks²

Percent

Mean

Variance

Standard Deviation

Coefficient of Variation

2007

42

15.79%

26.6

237.16

15.40

0.58

2008

40

15.04%

179.56

13.40

0.50

2009

29

10.90%

5.76

2.40

0.09

2010

19

7.14%

57.76

7.60

0.29

2011

10

3.76%

275.56

16.60

0.62

2012

27

10.15%

0.16

0.40

0.02

2013

31

11.65%

19.36

4.40

0.17

2014

18

6.77%

73.96

8.60

0.32

2015

14

5.26%

158.76

12.60

0.47

2016

36

13.53%

88.36

9.40

0.35

Sum

266

Average

109.64

10.47

0.39