The Q Ratio is a popular method of estimating the fair value of the stock market developed by Nobel Laureate James Tobin. It's a fairly simple concept, but laborious to calculate. The Q Ratio is the total price of the market divided by the replacement cost of all its companies. Fortunately, the government does the work of accumulating the data for the calculation. The numbers are supplied in the Federal Reserve Z.1 Financial Accounts of the United States of the United States, which is released quarterly.

Extrapolating Q

The ratio subsequent to the latest Fed data (through 2017 Q4) is based on a subjective process that factors in the monthly closes for the Vanguard Total Market ETF (VTI).

Unfortunately, the Q Ratio isn't a very timely metric. The Z.1 data is over two months old when it's released, and three additional months will pass before the next release. To address this problem, our monthly updates include an estimate for the more recent months based on changes in the VTI price (the Vanguard Total Market ETF) as a surrogate for Corporate Equities; Liability.

The first chart shows Q Ratio from 1900 to the present.

Interpreting the Ratio

The data since 1945 is a simple calculation using data from the Federal Reserve Z.1 Statistical Release, section B.103, Balance Sheet and Reconciliation Tables for Nonfinancial Corporate Business

The average (arithmetic mean) Q Ratio is about 0.69. The chart below shows the Q Ratio relative to its arithmetic mean of 1 (i.e., divided the ratio data points by the average). This gives a more intuitive sense to the numbers. For example, the all-time Q Ratio high at the peak of the Tech Bubble was 1.61 — which suggests that the market price was 136% above the historic average of replacement cost. The all-time lows in 1921, 1932 and 1982 were around 0.30, which is approximately 55% below replacement cost. That's quite a range. The latest data point is 65% above the mean and now in the vicinity of the range of the historic peaks that preceded the Tech Bubble.