Soon after implementation, I feel that companies would like to reduce pay as well. Maybe not by 20%, but it's an easy way to increase profitability.
People talking about macroeconomics often talk about how markets respond to certain pressures - as this gets further from the academics it gets watered down and that response is assumed to be instantaneous - but it isn't. In theory a payroll tax on the employer and income tax on the employee have the same long term economic outcomes - in practice that long term realization takes so long to work through the system that the effects of decreased take home usually end up being swallowed many times over by inflation before anyone feels any affect of it.
So I'd take a look at senior employees which tend to be a pretty curmudgeonly bunch that have been through wage freezes and non-monetary compensation circuses before and will jump ship if they get a wiff of it happening again. Companies won't feel any loss of revenue for a few years after work weeks are slashed - it takes a while for consumer spending to adjust to lower income - instead we'd likely eat a fair bit of inflation (which has been unhealthily stagnate for a while now) and everything would move on from there.
If the companies are responding to a natural decrease in effective revenue it'll be staggered and upstream companies will be shielded from it for longer - so you'll likely see a value shift from customer facing companies to B2B companies aaaaand - any wage slashing that goes on will just reinforce that value shift as valuable employees jump ship.
All these ripples that go through the economy do so slowly - and no MBA worth their salt is going to say (on the monday after switching to a reduced workweek) "Welp all our employees know this will eventually impact us so lets just slash their wages now". No, they'll wait and see if their business is able to ride out the shifting terrain without decreasing wages since that's a more stable approach and puts the company at less danger - and if that company happens to need to adjust employee costs it won't be evident until multi-year contracts are re-negotiated to lower rates and customers refuse to renew since their pocketbooks are empty.
Economics moves sloooow - maybe it'd be better to imagine the invisible snail of the market!
You mean, as long as we're personally beyond entry-level? My own career and compensation isn't my only concern.
I hasn't really thought about the zero experience folk though - thanks for mentioning it!
Later, I learned that full time employment is 35 hours, and insurance/benefits for part-time work gets really complicated for the stupidest of reasons. So despite the stupid responses, employers actually do have some obstacles to overcome even if they want to implement shorter weeks.