Even the most ardent of bulls would 'admit' that the period of the last 90s was a bubble in US equities. What started at the margin quickly morphed into a euphoric valuation for any and everything that could be pitched. Even The Fed's Jim Bullard 'knew' there was a bubble back then... Today's recovery of the NASDAQ to 4,000 - levels not seen since this period - is quickly dismissed by those that need things to go higher on the basis of earnings, multiples, or some such forward-looking hope-based methodology that reinforces their bias. However, Tobin's Q--among the longest-lived and most well-respected of longer-term valuation methodologies--has just reached levels only ever seen during the 1999/2000 bubble. BTFATH valuation?

Doug Short provides more color here...

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.

Source: Doug Short's Advisor Perspectives