Stock market concentration has reached 1800s levels:

Information Technology & Communications stocks now reflect a record 45% of total US market cap.

This percentage has DOUBLED over the last 10 years.

Tech is now larger than Energy & Materials, which together accounted for 41% of the market at their 1950s peak.

The last time any industry had such dominance was the transport sector in the 1880s.

In other words, the market is the least diversified in ~140 years.

Technology stocks effectively are the stock market.