In this subgroup, data on internal migration (inflow/outflow) for Poland in total (including for towns in general) and for the voivodships: Dolnośląskie, Łódzkie, Mazowieckie and Wielkopolskie (in total and in towns) take also into account migration within the cities (between districts), which took place in: Wrocław, Łódź, Warsaw and Poznań. Therefore, these data differ from the information presented in detailed tables concerning internal migration. In the case of tables of population, vital statistics and migration since 2015 are published balance only for the first half and year. There are not disseminated quarterly tables about the population (quarter 1, 2, 3, 4 and 1-3). The reason for the lack of quarterly tables are delays in the transfer of data from Registration Civil Office to the statistics, and consequently the lack for each quarter of full information on the number of facts of vital statistics and migration. These delay are caused by the implementation (since March 2015), a new system of the Ministry of Interior for the registration of civil status acts (computer system Źródło). Regarding insufficient quality of the data on international migration for permanent residence for 2015, the data on such migration, as well as data on long-term migration are not published.