In that peculiar circumstance we decided to do without the productivity and taxes that these people would pay.
The economy was benefiting from selling a lot of war materiel to the English already, I doubt that the availability of houses and furniture at bargain rates was really a great boon in comparison.
If it was even a benefit in comparison to the lost productivity at all, the next few years were ones of extreme labor shortage.
Perhaps we locked up a few spies, when we locked up all those Italian, German and Japanese immigrants and citizens. How many spies could there have been ?
That isn't measured, but it is the only realistic excuse there is.