Years

Duration

2004

2007

2008

2009

Khi²

p

≤7

161 (76.7%)

205 (83.3%)

251 (82.8%)

231 (86.2%)

6.15

0.01

8 - 14

47 (22.4%)

35 (14.2%)

40 (13.2%)

32 (11.9%)

1.47

0.22

>14

2 (01.0%)

6 (02.4%)

12 (04.0%)

5 (01.9%)

1.61

0.29

Total

210 (100.0%)

246 (100.0%)

303 (100.0%)

268 (100.0%)