Wealthier individuals typically have larger portions of their assets in the stock market, while middle-income households hold more wealth in real estate.

Elon Musk has a long history of making big promises — and Tesla investors used to be OK with that. Has something changed?

You could fall asleep and wake up at your destination,” said Mr. Musk, Tesla’s C.E.O., but some experts are skeptical that such cars will be ferrying passengers soon.