This brief presents preliminary estimates from the 2020/21 update of the Database on Immigrants in OECD Countries (DIOC), which reveal some unprecedented developments and cast a new light on structural trends revealed in previous datasets. Data by countries of origin for about a third of OECD countries covered have been estimated based on observed migrant stocks. Data by detailed countries of origin, including in terms of emigration rates, will be released later in 2024 based on a consolidated version of the DIOC data base for 2020/21.