Yes you’re right that real GDP fell by about 26–30% from its peak during the Great Depression which is slightly less than “nearly half.”
As for the unemployment part, national averages never reached 50% but some local communities like industrial cities saw much higher unemployment rates. For example Cleveland hit around 50% and Toledo (Ohio) reached as high as 80% during the early 1930s.
So the “up to 50%” talks about the extreme hardship in certain regions rather than the U.S. as a whole.
