I’ve heard a lot about it but is there a straight forward explanation for why it doesn’t appear in the aggregate data.

from 1890 until at least 2008 its not clear that GDP per capita altered its long term growth path. If you put your hand over the Great Depression and the War Boom would you suspect that anything special had happened during this period?

It was clearly a rough period for those who lived through it but by all appearances once the storm had long passed the seas were calm once again.

Indeed, in terms of affecting the long run trend in living standards it seems like the small, brief, but lasting speed-up of the 1960s was the bigger deal.