But how many of the 793,000 will be here next year, and as refugees in need of help? Some will have moved on, some will have been refused, others will obtain a different status by getting a job or marriage or whatever. You cannot simply add the numbers of each year's inflow.

the point being made is that to sustain these flows for significant spans of years would require the source nations to be emptied. Not just the educated elites, but the entire populations would have to up stakes.