I made a graph trying to visualize this. It's interesting to see the booms and busts in the past. 3 lines, blue is the total number built that year (500 ft minimum), red is NYC alone, and yellow is 1000 footers. All data is straight from SSP's database. I expect the future years won't be quite as dramatic as construction is unpredictable, but we are certainly poised to add a lot in the coming years.
Let me know if you have any questions!