Table 1.

Characteristics of practices by years took part in the vaccination study

	Years provided vaccination records used in analyses
	1997–1999	2000	1997–2000	None
Jarman tertile
Low	3	3	16	13
Med	7	2	16	8
High	1	2	23	12
SMR tertile
Low	2	2	18	10
Med	3	2	19	11
High	6	3	18	12
List size
<5000	3	0	20	10
5000 or more	8	7	35	23
Number of GPs
<7	10	6	51	31
7 or more	1	1	4	2
	11	7	55	33