Source: Federal Reserve Board, Distributional Financial Accounts; Bureau of Economic Analysis; calculations by Board staff. 2018:Q4  2018 dollars 400,000  Figure 7.
The exit of a member country would inevitably lead economic actors to wonder who would be next, with all the potential destabilising effects that such speculation could entail. The genie will not be put back in its bottle once and for all until it is clear that such a risk will not rear its head again.