How many refugees and migrants died trying to reach Europe? Joint population size and total estimation

We address the problem of estimating the number of migrants and refugees that died while trying to enter the European Union, during a period of twenty-five years. Only a subset of attempts with at least one casualty are reported by at least one media source. In order to obtain the estimate we propose a regression-extrapolation approach, for joint estimation of population size (here, the number of deadly individual or group attempts) and the sum of an accompanying trait (here, the number of deaths) over the population. The trait is measured only for a biased sample of individuals, that are repeatedly observed. Closed form expressions are derived for the estimator and its standard error. Our findings are that about forty-thousand have died from January 1993 to March 2019, during about fifty-five hundred attempts to enter the European Union. The number of deaths has been steadily increasing over time, and so has the number of deaths per attempt. About 20% of attempts with at least one casualty have not been recorded by any media source, and slightly less than 10% of deaths have thus been overlooked by media.