Data collection has been the Achilles heel of all research endeavors. Proper data can be hard to find, acquiring it is often prohibitively expensive and cleaning everything up is time-consuming.

This report presents estimates of the number of unauthorized immigrants in the United States as of July 2023 and for earlier years. As noted earlier in this report, the estimates presented here ...

Pew Research Center designed this study to assess the current state of online survey sampling methods – both probability-based and opt-in – and determine their accuracy on general population estimates ...

Andrew J Tatem works for the University of Southampton, and is Director of WorldPop. His research on mapping populations has been funded by donors such as the Gates Foundation, Wellcome Trust, GAVI.