Might be misleading as they changed the way the unemployed are counted several times I believe. In the 20s &30s if you were not working you were counted as unemployed - total number of able bodied divided into number of same working = rate
Of course, if you trust your government not to play with the numbers and to report honestly, then, well, the data must be correct ...
Data from the 20s and 30s was presented, but not used for this workup.