Comment by gustavus

I've heard multiple explanations, some of them include.

1. The moving off the gold standard

2. A large number of women started entering the workforce essentially doubling the supply of labor.

3. The rise of MBAs and downsizing really became big.

4. Outsourcing and off shoring started to be introduced during this time

5. The 70's stagflation where we say inflation and high interest rates.

These all seem to be plausible factors to me.