Aren’t buildings here always getting taller?

Yes, but not this fast.

In 1908, the Singer Building in Lower Manhattan became the first in the city to rise above 500 feet. Since then, only 26 percent of buildings of that heigh t were for residential use, according to the council.

[Read more about the transforming skyline.]

Since 2010, 64 percent of buildings (including those under construction) have been residential, most of them containing luxury condos, the council said.

Why are buildings getting taller?

One reason is technology.

Stronger concrete, faster and more efficient elevators, and sophisticated computer modeling have allowed developers to build taller and skinnier on sites that used to require much wider bases, according to Stephen V. DeSimone, the chief executive of DeSimone Consulting Engineers, who has worked on a number of new supertall buildings.

Another reason is money.

Residential megatowers are becoming more common, marking what Mr. Chen called “a major shift from a skyline dominated by office space and executive suites to one increasingly focused on securing the best views for well-heeled residents.”

And well-heeled residents, apparently, want a room with a view.

“You can’t even start residential occupancy below 20 floors in a lot of these buildings, because the view has already been blocked,” said Daniel Safarik, an editor with the Council on Tall Buildings and Urban Habitat.

Does the city regulate building heights?

Very much so.

Practically every inch of land in New York City falls into a zone that determines what kind of building can go there. Developers or landowners are sometimes granted waivers from those rules.

Lately, more developers are buying the unused development potential, or air rights, of adjacent properties to amass a larger building, Mr. Chen wrote.