%. ▁ ▁Norway ▁A ▁ 2 0 0 9 ▁study ▁in ▁Norway ▁reported ▁pre val ence ▁rates ▁for ▁AS D ▁r anging ▁from ▁ 0 . 2 1 % ▁to ▁ 0 . 8 7 %, ▁depending ▁on ▁assess ment ▁method ▁and ▁assumptions ▁about ▁non - response , ▁suggesting ▁that ▁method ological ▁factors ▁explain ▁large ▁var ian ces ▁in ▁pre val ence ▁rates ▁in ▁different ▁studies . ▁ ▁United ▁Kingdom ▁The ▁inc idence ▁and ▁changes ▁in ▁inc idence ▁with ▁time ▁are ▁unclear ▁in ▁the ▁United ▁Kingdom . ▁The ▁reported ▁aut ism ▁inc idence ▁in ▁the ▁UK ▁rose ▁starting ▁before ▁the ▁first ▁introduction ▁of ▁the ▁M MR ▁v acc ine ▁in ▁ 1 9 8 9 . ▁However , ▁a ▁perce ived ▁link ▁between ▁the ▁two ▁ar ising ▁from ▁the ▁results ▁of ▁a ▁fra ud ul ent ▁scientific ▁study ▁has ▁caused ▁considerable ▁controvers y , ▁despite ▁being ▁subsequently ▁dis pro ved . ▁A ▁ 2 0 0 4 ▁study ▁found ▁that ▁the ▁reported ▁inc idence ▁of ▁per vas ive ▁development al ▁dis orders ▁in ▁a ▁general ▁practice ▁research ▁database ▁in ▁England ▁and ▁Wales ▁grew ▁stead ily ▁during ▁ 1 9 8 8 – 2 0 0 1 ▁from ▁ 0 . 1 1 ▁to ▁ 2 . 9 8 ▁per ▁ 1 0 , 0 0 0 ▁person - year s , ▁and ▁concluded ▁that ▁much ▁of ▁this ▁increase ▁may ▁be ▁due ▁to ▁changes ▁in ▁di agnostic ▁practice . ▁ ▁Gen et ics ▁ ▁As ▁late ▁as ▁the ▁mid - 1 9 7 0