By Warren Buffett’s criteria, current stock prices are their most overvalued at least since World War II. In the chart below, the ratio of stock-market value, represented by the Wilshire 5000 index of all public stocks, to GDP is over 25 percent above the previous all-time high, the peak of the NASDAQ stock market bubble in 2000, which is indexed as 100 in the chart. The seemingly relentless rise of the stock market coincides with central-bank balance sheets that have continued to balloon since the Great Financial Crisis. While the major central banks generally do not target stock-market levels directly, a goal of their policies has been to push financial markets towards riskier investments, which, of course, include stocks. Global financial markets are interlinked, so that the actions of international central banks can affect what goes on in the U.S. and vice versa. The following chart compares securities holdings of the major central banks to the level of the U.S. stock market. There is close correspondence between the stock market-level and central-bank securities holdings, but both would be expected to grow with GDP, so the next chart compares the ratio of stock-market valuation to GDP in the first chart with a similar GDP ratio for central-bank assets. As central-bank holdings of debt climb relative to GDP, stock valuations soar in line. Some analysts, including the Fed, cite low real (after inflation) interest rates as justification for high stock valuations. Interest rates certainly affect the market in the short-term, as recently experienced, but, over the long-term, the correlation between real rates and the stock valuation measure in the chart above is less than half that of the liquidity provided by central bank securities purchases. Stocks’ overvaluation is evident to experienced investors scouring markets for historically reasonable values. Meanwhile, the GameStop saga (and there are plenty of other examples to choose from) are uncomfortably reminiscent of some of the excesses of the dotcom bubble. Just because the stock market is overvalued doesn’t mean it can’t get further overvalued. The next chart compares the U.S. stock market for the last decade with the NASDAQ bubble of the 1990s and the Japanese stock market bubble that crashed in the 1990s. While U.S. stocks currently are at Buffett ratio all-time highs, the NASDAQ and Japanese bubbles rose even further from their starting points. The current bubble may do so as well if central banks keep pouring liquidity into the financial markets. What’s clear from the first chart is that the stock-market downturn from the NASDAQ bubble preceded and contributed to the 2000 recession, as has been acknowledged by Fed chair Jerome Powell. The Japanese bubble’s bursting was also linked to a recession. Stocks are an insignificant holding of the U.S. banking system, however, which was largely unaffected by the NASDAQ bubble, although Japanese banks with extensive crossholdings were crippled for years. Posing a greater financial risk than a stock downturn is that historically high valuations permeate the entire financial system. The U.S. stock market is a bellwether for risky assets globally. Differences between borrowing rates for the U.S. government and high-quality investment grade borrowers have fallen significantly and are quite low historically. Rates for the riskiest sub-investment grade “junk bond” borrowers are at all time lows. Future bond market turmoil from the inevitable reversal of maximally easy monetary conditions may pose a threat to financial stability, but the biggest risk to the financial system is a housing downturn, as happened in the Great Financial Crisis. Real estate is the single largest component of banking assets. Fortunately, as illustrated in the following chart, which compares housing prices to income, real-estate values are about 20 percent lower than the overextended levels from the GFC era. Unfortunately, a recent rapid appreciation of housing prices may alter this favorable balance. The chart below shows housing prices appreciating faster than personal incomes by an annualized 20 percent, the fastest such rate recorded. Of course, there is a large rebound following the pandemic, but, should this rate continue, it won’t be long before housing is flashing critical warning signs. The Fed’s December plan was to hold rates at rock bottom levels until unemployment is minimized and inflation surpasses 2 percent, which they expected to take 3 years. Should housing prices continue to appreciate at recent rates, three more years of maximum stimulus would put them well into the GFC danger zone. The pandemic recovery is moving faster than the Fed and many other forecasters expected. In March 2020, the Fed forecast a 6.5 percent decline for the year. Forecasters surveyed in May by the Philadelphia Fed expected a 5.6 percent decline. 2020’s downturn was 3.5 percent, and these same forecasters expect growth over 4 percent for 2021, so overall recovery is in sight. The financial markets are already beginning to bring forward their expectations of when the Fed will begin raising rates (about two years), and it would not surprise if this start anticipating an even closer date in due course. . More years of maximum stimulus would further inflate the stock market bubble and possibly create an even more lethal housing bubble as well. The Fed has been determined to see unemployment all the way down before any tightening, a worthy goal, but even a mild downturn in the wake of a bursting the stock market bubble would have grave consequences following so closely after the pandemic. Creation of another housing bubble would be catastrophic. Depressed business and labor sectors may not fully recover this year, but all the monetary stimulus in the world won’t convert airplanes, bars, and restaurants into homes, nor flight crew and serving staff into home builders, nor into other booming sectors. When the pandemic permits, cash savings are extremely high, and there is plenty of pent-up demand for these people and their services. Single-minded focus on just one goal ignores monetary policy’s significant time lags and complex effects throughout an economy. Now is the time for the Fed to plan to stabilize policy and the markets, and this must be carefully communicated and executed to minimize volatility such as 2013’s “taper tantrum.” While inflation may pop up in the short-term as recovery continues, long-term inflation has been in forty-year decline, so it is unlikely to pose a major problem. The biggest economic risk is financial instability, and, despite its great initial work stanching the pandemic panic, right now the biggest financial instability risk is. . . the Fed.