Population growth alone would require another 600 medallions. But remember: in the 1930s, we were just coming out (or on the upswing) of the Great Recession; so affluence would dictate a much larger number. So why is the number so low?
> Instead, arcane aspects of state and local law and, crucially, the power wielded by wealthy and politically generous fleet owners — who don’t want to see the creation of more medallions lest the value of theirs decline — make that [more medallions] virtually impossible.
There you have it. It is, for the lack of a better word, greed. When you have hedgefunds owning medallions[1], you know it's a bad sign. Essential services for the general populace should not be a vehicle for hedge funds.
An ideal (or, a better) system would be responsive. It would look at how busy cabs are, and accordingly change the number of medallions in circulation. Every year (or every nth year, take your pick), have a Dutch auction[2] of the desired number of medallions. Disallow renting of medallions (only the owner gets to drive the cab), which will kill speculation. Put an app around the whole system, so users can hail cabs from their mobile devices. Pain eased.
[1] http://www.wsj.com/articles/SB100014240527023036530045792143...