Table 3.

Results of the log-rank tests for equality of survivor functions.

Variable	Chi-squared	P-value
First WHT status in 2012	3,008.9	<0.001
Season in which 2012 WHT took place	8.51	0.037
Number of incidents in the previous 10 years	2,635.7	<0.001
Geographical risk area	1,238.86	<0.001
Herd type	1,535.93	<0.001
Herd size	4,388.12	<0.001
Annual rolling county level incidence at end of 2012	1,207.05	<0.001