The blog Urbanomics has a comparison of the current AI investment concentration to the 19th century railroad investment boom in England and the United States. In this particular case, the blogger neglected to provide the original source, which he or she normally does. Financial Times and Economist are typical sources. Anyway, here are some stats mentioned:

• Peak “railway mania” in the UK was around the 1840s, and railroad investment accounted for around half of all investment at that time.
• Between about 1830 and 1870 in the UK, railroad investment accounted for about 20% of all investment.
• In the US, episodic railroad investment booms occurred in the 1840s and 1870s. Railroad investment at these times was around 40% of all investment. This accounted for GDP growth of about 6-10%.
• The brief clip actually doesn’t tell us how much of total US investment in 2025 is directed to AI. But it accounts for GDP growth of around 2%.

These are interesting numbers, but I don’t think comparing 19th century and 21st century US GDP growth is a very good comparison. That is essentially comparing a fast-growing developing country to a slow-growing advanced economy. If I had to pick one or the other to live in, I would probably go with the one that has safe drinking water, antibiotics, vaccinations, relatively painless dentistry, and air conditioning.