The Tobin's Q is the ratio of price to replacement cost, which is in many ways similar to book value. It was developed by Economic Nobel laureate James Tobin in the 1960s as a metric for valuing the stock market.
The Q ratio can be calculated from the most recent Federal Reserve Flow of Funds release. The ratio is calculated by dividing line 35 of table B.102 by line 32. The historical data is also available on the St. Louis FRED website. However, because the Flow of Funds report is released long after the quarter end, we update the Q ratio for the change in stock prices since the most recent flow of funds report.