I wish the article went more in depth on potential causes. I suspect the dominant factor is the expectations of the largest industries in the city, but that's

I wish the article went more in depth on potential causes. I suspect the dominant factor is the expectations of the largest industries in the city, but that's only mentioned for military towns. To give an example: as a Seattleite, I was initially surprised to see how much earlier the average starting time is compared to San Francisco or San Jose. However, I think the relatively early start times at, say, Boeing are an effective offset to the later start times at Microsoft and Amazon, and this likely accounts for most of the difference.