Table 1.

Number and percentage of herds that had a subsequent incident, stratified by each explanatory variable.

Variable	N	Missing	Herds with a subsequent incident
			n	%	95% CIa
FIRST WHT STATUS IN 2012
Clear	27,289	0	7,231	26.5	26.0–27.0
IRs Only	3,311		2,095	63.3	61.6–64.9
SEASON IN WHICH 2012 WHT TOOK PLACE
Spring	9,935	0	2,976	30.0	29.1–30.9
Summer	3,996		1,198	30.0	28.6–31.4
Autumn	7,474		2,253	30.1	29.1–31.2
Winter	9,195		2,899	31.5	30.6–32.5
NUMBER OF INCIDENTS IN THE PREVIOUS 10 YEARS
0–2	27,639	0	7,376	26.7	26.2–27.2
3 or more	2,961		1,950	65.9	64.1–67.5
GEOGRAPHICAL RISK AREA
England high-risk	17,145	0	6,595	38.5	37.7–39.2
England Edge	3,311		636	19.2	17.9–20.5
Wales	10,144		2,095	20.7	19.9–21.5
ANNUAL ROLLING COUNTY LEVEL INCIDENCE AT THE END OF 2012
0–14.6 per 100 herd years at risk	17,431	0	3,983	22.9	22.2–23.5
>14.6 per 100 herd years at risk	13,169		5,343	40.6	39.7–41.4
HERD TYPE
Beef	23,713	0	6,087	25.7	25.1–26.2
Dairy	6,447		3,189	49.5	48.3–50.7
Other	440		50	11.4	8.7–14.7
HERD SIZE
0–10	4,941	1,563	453	9.2	8.4–10.0
11–50	8,697		1,755	20.2	19.4–21.0
51–100	5,488		1,802	32.8	31.6–34.1
101–200	5,164		2,336	45.2	43.9–46.6
201–300	2,196		1,218	55.5	53.4–57.5
>300	2,551		1,700	66.6	64.8–68.4

^aConfidence interval.