Another interesting fact about skyscrapers is they tend to mark the tops of economic expansion. This means that for every big building you see, there's a good likelyhood it was built just before an economic downturn.

For instance, the Empire State Building in New York City was called "Empty State" because of the great depression, no one would rent spaces in it. The recent spate of big building projects tends to signal misallocation of capital in an easy borrowing environment.

This will change, of course. The stairs go up, the elevator goes down :)