I've put together a chart which shows what American and Canadian cities have built the highest percentage of skyscrapers, defined here as 250 ft/76 meters, since the year 2000. To qualify for the list cities must have 10 buildings over 250 feet. Please let me know if you notice any omissions.
On average, the cities included here have built about 1/3rd of their skyscrapers since 2000. This first chart shows cities which have fallen below that mark,
All 5 cities that haven't built anything in the past 20 years already have very few, less than 15 each. New Orleans is fairly notable, it has built a good number but has seen very little development in the past decade. A lot of the cities on this list are probably not surprising, midwest rust belt, flyer over type places make up a good majority. However, some of the largest cities in the nation like New York, Phoenix, San Francisco and Houston do fall below average, but not by much. Los Angeles is a bit of an outlier, although it has built a large number the overall percentage is not as high as many peers.
Here are the cities that have performed above average. Coquitlam takes the unique distinction of being the only place with 100%, with other Toronto and Vancouver suburbs being high. Miami leads the big US cities, especially impressive given Miami's already high stock of skyscrapers before 2000 (In fact, Miami had the 4th highest total number built, behind only Toronto, NYC and Chicago). Several Miami suburbs also appear on the list. Alberta cities doing well. Austin is probably no surprise.
Edit - updated to include Aventura, Oakland, St. Paul, Arlington VA, San Jose PR, and Bellevue WA.