Timeline of the Swedish Inpatient Register. Years inside the arrow indicate the first year when an ICD classification was in use. ICD-10 was introduced in 1997, with the exception of the county of Skåne where ICD-9 was still in use throughout 1997. The one-year delay in introducing ICD-10 in Skåne has some implications when identifying patients with a certain disease/disorder in this county because about 8-9% of the Swedish population live in Skåne.
Ludvigsson et al. BMC Public Health 2011 11:450 doi:10.1186/1471-2458-11-450