For example, the critical mass was estimated to be 3 000 residents in Luxemburg and 5 000-6 000 inhabitants in Estonia (per the recommendations that an administrative reform expert committee put forward in November 2015), but 10 000-20 000 residents in Norway (per the 2014 ad hoc expert committee appointed by the government), and 20 000 residents in Finland during the PARAS reform (only for primary' healthcare and related services - compared with 50 000 residents for vocational education, for example). In the case of Finland, the methodology used to identify an optimal threshold was criticised and the legislation was changed in 2011 to include more diverse criteria. Linguistic and/or cultural particularities may also be taken into account (e.g. in Estonia, Finland, Greece, Iceland, etc.). For example, in the United States, a wide variety of “special districts” (as opposed to general purpose local governments) provide a single public service (or a set of related public services) to the residents of a determined area.