So when gold moves up in value in dollars, that’s merely a sign that the dollar’s purchasing power is shrinking. Though President Richard Nixon delinked the dollar from 1/35^th of a gold ounce peg for good in 1973, he didn’t erase the gold signal. His move signaled that the Nixon administration wanted a weaker dollar. Markets complied. The dollar price of gold rose throughout the 1970s under Presidents Nixon, Ford and Carter. The economy performed badly, at least by U.S. standards. That it did was a blinding glimpse of the obvious.

To understand why, never forget that no one earns money. They earn what money can be exchanged for. The dollar’s devaluation in the 1970s signaled a major tax on work simply because the dollars earned while working were exchangeable for fewer and fewer market goods.

For businesses, much the same was at work. To this day it’s assumed that devaluation improves prospects for businesses. No, they earn dollars. Devaluation shrinks the value of their earnings. After which, no business creates products or services without global cooperation. Something as basic as the pencil is a consequence of global production.

If the dollar is devalued, the dollar cost of production increases. A statement of the obvious. Currency devaluation is an explicit acknowledgement that the currency commands fewer market goods, which means the dollar cost of production rises.

And then there is investment; the driver of economic progress. Investors invest by purchasing shares or lending money, but no one invests dollars; rather they shift resources to someone else or some other corporation in the hope of attaining greater resource access (an investment return) in the future. In other words, they hope to get back more wealth than they committed to said venture. But if the dollar is devalued, so by definition are investment returns devalued. Investment is what enables greater productivity among those who comprise any economy, but if policy favors devaluation, investment becomes less enticing.

If the currency is in decline, as in if monetary authorities are shrinking its exchangeable value, there’s a tendency to protect what’s being devalued. Translated, investors hedge against inflation, which is currency devaluation.

More specifically, when currencies are being devalued there’s a tendency among investors to consume hard assets (think land, housing, rare stamps, art), or wealth that already exists, instead of investing in stocks and bonds; both claims on wealth that doesn’t yet exist. Wealth that already exists is more of a sure thing than claims on what might eventually amount to wealth.

Looked at in terms of the dollar and gold, the dollar has always merely been a measure of wealth facilitating the exchange of the goods, services and labor that represent real wealth. And while the dollar is still the world’s currency, the measure has shrunk substantially since the 1970s versus the constant that is gold.

During weak dollar stretches since 1973, a great deal more money has found its way into hard assets like land, housing, rare stamps, art, gold, and other commodities least vulnerable to the dollar’s decline. Translated, wealth that already exists does best during periods of devaluation. Think the 1970s. Think the 2000s. Investment, which is the purchase of uncertain future returns, doesn’t do as well during periods of devaluation. Why risk stretching for uncertain returns if, assuming you get them, they come back in dollars exchangeable for fewer and fewer goods, services, and labor?

Fast forward to the present, Donald Trump has made plain since before he was president that he wanted a weaker dollar. Currency markets have complied over time. As previously mentioned, a dollar purchased 1/1200^th of an ounce of gold in January of 2017 when Trump was inaugurated. Its value has slowly declined ever since.

The decline hasn’t crushed the economy, but it’s made the purchase of existing wealth like housing more and more attractive a la the 1970s and the 2000s. People have been consuming wealth that already exists in slowly higher amounts over investment in the creation of future wealth. This is the definition of slower growth. Consumption is the easy part. It’s the abstinence that drives progress as new ideas are invested in.

Right now the yellow metal is at all-time highs. Which means the dollar is at all-time lows. This will slow investment, and with it, the economy. If it continues, it will destroy the economic portion of Trump’s presidency much as it did those of Nixon, Carter, Bush 43, and Obama.

John Tamny is editor of RealClearMarkets, Vice President at FreedomWorks, and a senior economic adviser to Toreador Research and Trading (www.trtadvisors.com). His new book is titled They’re Both Wrong: A Policy Guide for America’s Frustrated Independent Thinkers. Other books by Tamny include The End of Work, about the exciting growth of jobs more and more of us love, Who Needs the Fed? and Popular Economics. He can be reached at jtamny@realclearmarkets.com.

This article originally appeared on RealClearMarkets.