Table 1.

The reduced KVB dataset compared to the respective Bavarian birth cohorts and causes for the observed differences.

	percent	N
Bavarian birth cohorts (1.10.2001–31.12.2002) [9]	100	142,809
Reduced KVB dataset	78	111,977
difference		30,832
Reasons:
privately insured+	10.0	14,281
change of insurance*	5.0–8.0	7,140–11,425
no consultancy of outpatient physician in 1st 6 months and 2nd year of life*	4.9	6,998
moving from Bavaria [9]	1.4	1,999

* estimated from AOK Bavaria data (own data)

⁺ personal communication of Dr. Frank Niehaus, WIP-PKV (scientific Institute of the Private Health Insurances)