The aim of this study was to develop a methodological tool to ‘nowcast’ migrant stocks by using real-time data from the Facebook Marketing Application Programming Interface (API) and official migration data from EU member states and states in the United States. To achieve this, two specific objectives were set:

To collect real-time data that could provide estimates of migrant stocks in the countries of interest from the Facebook Marketing API, along with migrant-stocks data from official sources from 2010 onwards (including meta information about the quality of these data).  

To develop a Bayesian model capable of combining real-time data from the Facebook Marketing API and official migration data to nowcast stocks of migrants in EU member states and US states, and test the model in some corridors, using real-world data. This approach built on similar research undertaken by RAND to develop a proof-of-concept for nowcasting labour mobility within the EU.