Demographics of Poland
According to GUS, about 38,325,000 people live in Poland, however, the same report states that the number of residents living in the country all the time is approximately 37,200,000; with 1,125,000 people living abroad for 6 to 7 months or more. It means that the permanent population may be correspondingly smaller.
Congress Poland
Originally, the Kingdom had an area of roughly 128,500 km and a population of approximately 3.3 million. The new state would be one of the smallest Polish states ever, smaller than the preceding Duchy of Warsaw and much smaller than the Polish-Lithuanian Commonwealth which had a population of 10 million and an area of 1 million km. Its population reached 6.1 million by 1870 and 10 million by 1900. Most of the ethnic Poles in the Russian Empire lived in the Congress Kingdom, although some areas outside it also contained a Polish majority.