NY-Newark is clearly the wrong metric, since the new housing website only covers NY. The comparable statistic is 8.4M for 2020: http://worldpopulationreview.com/us-cities/new-york-city-pop...
But I agree this isn't right either - you really want new commutable housing vs existing commutable housing, and that's obviously a lot bigger number on both sides of the equation, and because it affects multiple jurisdictions (NJ, CT, LI, etc) it would be a pain to gather properly... even assuming everyone could agree on "commutable" - for some, that means 20mins, for others 2hrs is fine sitting comfortably on LIRR, NJT or metro north; let alone capturing the impact of transfers, flaky vs reliable transit options, transit cost... I once commuted by LIRR: all fun and games until you're waiting for a train transfer outdoors in high wind in Feb, and then get to your car, which has thawed/refrozen and you need to excavate to even get in...)
hope this helps, please be gentle.