It's a combination of things.
or are the higher SEER ratings simply from the reduced amp draw of the ECM motors vs. the PSC motors?
It is my understanding that operating a compressor at lower capacity within a given system increases efficiency. Here's why: The compression ratio determines amp draw relative to capacity. Having oversized coils improves heat transfer, thus allowing a system to run lower head temperature and higher suction temperature; this results in a lower head pressure and higher suction pressure.
Your existing furnace control board most likely does not have separate relays and lead connections for two-speed cooling. (Blower speed must be reduced for second stage operation - if not, humidity removal will really suffer and it will be impossible to get the charge right for 1st stage operation) The installer would have to rig it with a relay to switch between 1st and 2nd stage cooling speeds. (Not recommended, blower speed still might be too high on 1st stage)
economic collapse is a certainty. debt based fiat currency monetary systems can never continue indefinitely because they require continuous creation of new debt to service the existing debt. in the absence of economical growth (which is always predicated on increased resource extraction rather than capital alone), this leads to massive inflation which destroys the currency.
your leaders can't fix this - they're corrupt and only exist to enrich themselves and their corporate friends.