>> as high as 10M
Sorry, I wasn’t clear. I meant yearly migrants. If every year fewer applications are processed then filed, it adds to the backlog. So the only information you get by looking at the backlog is total number of willing migrants. However they (or rather we, as I am personally one of the applicants in that backlog) are not gonna migrate here all at once, some are willing but not able (for whatever reason), some are old and no longer relevant, some are duplicate, etc.
In reality an open border policy would come gradually. So the number of yearly migrants would gradually grow, until it reaches a local peak and then slow down. Many willing people will delay their migration if they can’t find a job, etc.
So I pulled that lower bound of 1M from current migration trends. Last year it was about 700k but that was a covid year, so 1M is an easy guess of a lower bound. As for the upper bound I just took a wild guess... There is no way of knowing that number unless you do some extensive survey, and plug it into a computational model (I wonder if anyone has ever done that).
But honestly the actual number doesn’t actually matter. Societal modelling is a funny science with a lot of interacting variables. The current state of prohibitory migration actually affects the behavior of current migrants, if the migration would be free, the behavior would be different (think decriminalizing drugs).
My skepticism about the concerns people have for free migrations is that I actually see little evidence to warrant these concerns. People say stuff like: “puts a strain on society” without explaining how, or by showing evidence. Historically societies have grown by way more then 17% over a short period and did just fine. Currently the societies which are taking many migrants seem to handle it kind of well actually. There are rural communities in Iceland which grow by 30-40% in a single year by taking in 4-5 refugee families, and do just fine.
So given our evidence so far, I would say that any concerns about “opening up the floodgates” are unjustified.