When analysts make their estimates on the health of the U.S. economy, they look at trends in consumer purchases, savings rates — even railcars reserved this summer, months ahead of the Christmas rush.

But if we want to understand the forces shaping our national economy, even that’s not enough.

Take copper — a key indicator today of the health of our economy, and a staple of the much-hoped-for resurgence in American manufacturing.

What do we need to know if we want to read the signals copper is sending us?

We need to know whether Chilean copper miners will show up for work tomorrow — or whether they’ll call another snap-strike at the world’s largest copper mine, in the world’s largest copper-producing nation.

We need to know whether resource nationalists in Indonesia will demand a revision of the long-running mine license at that nation’s massive Grasberg gold mine — which generates sufficient copper by-product to count as the world’s second-largest copper mine.

In our interconnected economy, these questions are a reminder that forces far beyond our control can spike prices, slow supply and tip a fragile economic recovery back into recession — pulling millions of American families along for the ride.

The answer isn’t to retreat from the global marketplace in a vain attempt to insulate ourselves from the international economy. We can’t — and we shouldn’t. America is far richer for its openness to global markets.

As the examples cited here make clear, we can never control uncertainties beyond our borders. But with so much in the wider world outside our control, there is one step we can take: we can remove constraints to our own economic growth.

Put simply, if we want to put American manufacturing on a stronger, more stable footing, we need to start by providing the raw materials of manufacturing — metals and minerals — here at home.

As a case in point, consider Arizona — the Copper State. Today, two-thirds of all copper mined in the United States comes from Arizona alone.

Yet there remains a huge “copper gap” in the United States — an annual 600,000 metric ton shortfall between the copper we use and the metal produced in American mines. That hurts our economy, and even our national security — as the Department of Defense reports that a shortfall in copper supply has already led to “a significant weapon system production delay.”

And that gap leaves us exposed to the decisions of Chilean miners, Indonesian officials and dozens of other micro-forces at work in the global metals supply chain.

Worse still, the copper gap is of our own making. Take Arizona’s proposed Resolution Copper Mine, which awaits congressional action to approve the federal lands swap to let it move forward. At full production, Resolution could provide nearly enough copper to close our gap, taking us back to a place America hasn’t been for 20 years — providing at least 90 percent of all the copper we consume.

In a world of uncertainty, the U.S. needs surety of supply. Our Congress members have it in their power to open the path for production at Resolution Copper. When they act, it will be one less reason for the U.S. economy — and for the U.S. military — to be at the mercy of global forces beyond our control.

Daniel McGroarty is president of the nonprofit American Resources Policy Network.