"Average construction speed of skyscrapers completed in 2000 and 2020, in square feet per year"
While a bit unclear I take that to mean it's presenting the construction speed of individual skyscrapers and giving the measurements in square feet per year then averaging those rates by presented location. In this measurement a 200x200 square foot floor building with 20 stories would be 800k square feet, if it took 4 years to complete that would factor in as 200k/square feet per year in the city average, not as +200k/square feet per year to the bar.
Looking at the graphs it seems a building with 4,000,000 square feet doesn't take much longer than a building with 400,000 square feet: https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_pr... and there are a lot more smaller ones to weigh down the speed.
While a bit unclear I take that to mean it's presenting the construction speed of individual skyscrapers and giving the measurements in square feet per year then averaging those rates by presented location. In this measurement a 200x200 square foot floor building with 20 stories would be 800k square feet, if it took 4 years to complete that would factor in as 200k/square feet per year in the city average, not as +200k/square feet per year to the bar.
Looking at the graphs it seems a building with 4,000,000 square feet doesn't take much longer than a building with 400,000 square feet: https://substackcdn.com/image/fetch/f_auto,q_auto:good,fl_pr... and there are a lot more smaller ones to weigh down the speed.