Benzinga and Yahoo Finance LLC may earn commission or revenue on some items through the links below. Bank of America strategist Michael Hartnett has voiced concerns about a possible bubble in the AI stock market. This comes in light of valuation metrics reaching historic highs. Hartnett has pointed out the S&P 500’s price-to-book ratio, which is a valuation measure comparing the total market cap of the index’s constituents to their total assets minus liabilities. As of August, this ratio hit a record high ...