I have it on the authority of no less than COL David Hackworth that the US built about 61,000 ships during WWII. Sixty-one thousand! We haven’t got 61,000 howitzers anymore, probably! No one in Germany expected the might of the US industrial machine. I mocked him myself, said he couldn’t be serious, but he was. Actually I don’t know if he meant warships only or what.

So if 1600 ships out of say 15K/year that were built in 1942 (neglecting ships already built and neglecting the cumulative output), that’s only 10% of that year’s new shipping, not 20%. With existing ships it would be well under 5% at any time.