Investors are once again grappling with the implications of the ongoing surge in the stock market and whether this signals a potential bubble, particularly as discussions surrounding artificial intelligence (AI) continue to captivate analysts and traders alike. Bank of America strategist Michael Hartnett recently weighed in on this topic, presenting a range of concerning indicators in a note to clients.
Hartnett pointed out several critical markers that he believes warrant attention. Firstly, he noted the “exponential price action” observed in the stock market, coupled with low market volatility and high valuations that see the S&P 500’s 12-month trailing price-to-earnings (PE) ratio sitting in the high 20s. Another alarming trend is the extreme market concentration, where the top ten stocks account for approximately 40% of the S&P 500. Hartnett also highlighted that only 21 stocks within the S&P 500, representing about 4%, are currently at new highs, despite the index itself reaching record levels. For context, during the dot-com peak, around 20 stocks were at new highs. A startling 331 stocks in the S&P 500 are trading at least 20% below their all-time highs.
Moreover, Bank of America’s Bull/Bear Indicator has surged to 8.5, reflecting what the bank describes as “extreme bullish” sentiment—a situation they consider a contrarian sell signal. Hartnett identified the primary risk that could burst any potential bubble: the possibility of rate hikes by the Federal Reserve. He pointed out that as rising oil prices contribute to escalating inflation, the risk of rate hikes appears more imminent. According to the CME FedWatch tool, there is a 44% probability that the federal funds rate could increase by at least 25 basis points by December.
In light of these indicators, Hartnett provided clients with a “post-bubble investing playbook” based on historical precedents from previous market manias, such as the Roaring 20s, the dot-com bubble, Japan’s bubble in the 1980s, and China’s property boom around 2007. He suggested that the roadmap for investors emerging from a bubble since 1929 leans towards long bonds, as well as a mix of defensive sectors that have underperformed during the last stages of the bubble.
In practical terms for today’s investors, Hartnett recommended focusing on consumer staples, financials, and healthcare sectors, signaling that these areas are likely to outperform. Additionally, he noted that small-cap tech and growth stocks are better positioned as the AI narrative progresses, suggesting a shift towards benefiting from adoption rather than speculative trading.
Investors looking to align with Hartnett’s strategies may consider ETFs that offer exposure to these recommended sectors. For instance, the Vanguard Consumer Staples ETF (VDC), the iShares U.S. Financials ETF (IYF), the Health Care Select Sector SPDR Fund (XLV), and the Invesco S&P SmallCap Information Technology ETF (PSCT) are some examples that could fit into this revised investment strategy.
As the possibility of a bubble looms, these insights from Hartnett might serve as crucial guidance for investors navigating the unpredictable terrain of the current market climate.



