The index includes only tower cranes, which rise 10 to 80 stories and have long booms that lift steel and concrete for projects including hotels, condominiums, offices, stadiums, convention centers, arts complexes and schools. This winter, the tally came to 423.

The total has stayed relatively steady since the summer of 2015 (there were 439 cranes then), which was the crest of the current development wave, some brokers say. The index has remained consistent despite headwinds like climbing interest rates, trade turmoil, rising material costs and a tight labor market.

Seattle was the top city in the United States on the latest index, with 59 cranes. Only Toronto, one of two Canadian cities on the list (Calgary is the other), had more, with 104. In last place was Phoenix, with five.

Amazon is partly to thank for Seattle’s top ranking, which it has held for several years. After a flurry of development, the internet giant has transformed the South Lake Union neighborhood, a sleepy former warehouse district, into a dense office hub.

But other areas, like downtown, are awash in hammers and hard hats, too. “I’m looking out my window, and I’m seeing cranes everywhere,” said David Gurry , a senior vice president with the brokerage firm Colliers International there.

Typical real estate cycles run about eight years, Mr. Gurry said, but the current one, clocking in at 12 so far, still has legs. “Normally, I might be concerned to see so many cranes, because it might be a sign of overbuilding,” he said.

Housing is a huge driver of real estate construction. High-rise apartment buildings, which gained popularity a couple of decades ago, are increasingly common. But office buildings are also arriving in a resilient market. Seattle has 60 million square feet of office space, brokers say, a quarter of which is controlled by Amazon.