Investors are infatuated with price targets for gold and exchange traded funds tracking the precious metal, but many valuation techniques favored by analysts are faulty, says a portfolio manager at ETF provider State Street Global Advisors.

“I’m bullish on gold, but let’s just be intellectually honest on valuing it,” said State Street’s Chris Goolgasian at the recent Morningstar ETF Invest Conference in Chicago.

He also thinks gold is not in a bubble, citing supply constraints and skepticism over gold’s multiyear run.

However, Goolgasian is wary of Wall Street’s habit of looking at past ratios and historical performance and applying them to today’s market to slap a target price on gold. These approaches include inflation-adjusted targets from previous gold highs, or the ratio of gold to the U.S. monetary base or the Dow Jones Industrial Average.

“Those are interesting data points but they don’t provide a way to value gold,” he said. The portfolio manager is upbeat on gold but doesn’t do price targets.

One reason he’s bullish is that despite gold’s march higher, the supply hasn’t increased. In other words, miners haven’t been able to increase their output. This is a positive for gold because previous asset bubbles have popped when supply met demand. For example, the Nasdaq bubble popped after a frenzy of tech IPOS, while a surge in housing starts oversaturated the real estate market in the housing boom, Goolgasian argued.

Additionally, skepticism over the gold rally is another bullish sign, he said.