For most of the industrial era, a nation’s carbon emissions moved in lock step with its economy. Growth meant higher emissions. But over the past decade or so, that’s changed. Even as the global economy continued to grow, carbon emissions remained flat or dropped a bit.

It would be simple to ascribe this to the explosion in renewable energy, but reality is rarely so simple. Countries like China saw explosive growth in both renewables and fossil-fuel use; Germany and Japan expanded renewables even as they slashed nuclear power; and in the United States, the federal government has been MIA, leading to a chaotic mix of state and local efforts. So it’s worth taking a careful look into what exactly might be causing the drop in emissions.

That’s precisely what an international group of researchers has now done, analyzing what’s gone on in 79 countries, including some that have dropped emissions, and others that have not. The researchers find that renewable energy use is a big factor but so is reduced energy use overall. And, for both of these factors, government policy appears to play a large role.