Whooping cough cases per year (in thousands)

74.7
69.5
120.7
68.7
45
37.1
60.9
62.8
31.7
28.3
32.1
40
14.8
11.5
17.7
17.1
13
6.8
7.7
9.7
4.8
3.3
4.2
3
3.3
1.8
2.4
1.7
1
2.2
2.1
1.6
1.7
1.2
1.9
2.5
2.3
3.6
4.2
2.8
3.5
4.2
4.6
2.7
4.1
6.6
4.6
5.1
7.8
6.6
7.4
7.3
7.9
7.6
9.8
11.6
25.8
25.6
15.6
10.5
13.3
16.9
27.6
18.7
48.3
28.6
33
20.8
18
19
15.6
18.6
6.1
2.1
3
3.8
16.4