The United Kingdom's population growth is projected to slow dramatically in the next decade, largely due to lower assumptions about future fertility levels making net immigration a crucial variable over coming decades. The United Kingdom's population is projected to grow 3.2% to 69.2 million in the decade to 2030, up from 67.1 million in 2020. In the decade to 2020, the population grew by 4.3 million, or 6.9%.