Year

Number of Attacks¹

Percent

Mean

Variance

Standard Deviation

Coefficient of Variation

2007

0

0.00%

2.8

7.84

2.80

1.00

2008

1

3.57%

3.24

1.80

0.64

2009

2

7.14%

0.64

0.80

0.29

2010

0

0.00%

7.84

2.80

1.00

2011

0

0.00%

7.84

2.80

1.00

2012

15

53.57%

148.84

12.20

4.36

2013

7

25.00%

17.64

4.20

1.50

2014

2

7.14%

0.64

0.80

0.29

2015

0

0.00%

7.84

2.80

1.00

2016

1

3.57%

3.24

1.80

0.64

Sum

28

Average

20.56

4.53

1.62