With an economy roughly 50 percent larger than two decades ago – and with 50 million more energy consumers to boot – one might think our nation’s energy-related greenhouse gas emissions would be significantly higher today than back when Forrest Gump entertained moviegoers and Michael Jackson made headlines by wedding Elvis Presley’s daughter.

But they’re not.

In fact, U.S. carbon dioxide emissions fell 3.8 percent last year to levels not seen since 1994. According to data from the Energy Information Administration (EIA), energy-related carbon dioxide emissions have actually declined in five out of the last seven years.

A key reason for those dramatic statistics is simple: natural gas from shale.

The EIA reports that the growing use of cleaner-burning, lower-carbon natural gas in place of coal to generate power has “substantially reduced the carbon intensity of electricity generation in 2012.”  From 2007 to 2012, this measure of carbon intensity in power generation – traditionally the largest emitter of greenhouse gases – has fallen by 13 percent.

I’ll note that these developments were not prompted by any sort of national program, regulation, or public expenditure from Washington.

They are due to the abundance of natural gas brought on by advances in hydraulic fracturing and directional drilling. This increase in U.S. energy supplies is also revitalizing domestic manufacturing and is providing one of the few sparks of life in the American economy.

In September, I pointed to a study compiled by T2 & Associates for the American Petroleum Institute.  It reported that the U.S.-based oil and gas industry invested more than $165 billion between 2000 and 2012 in technologies that helped reduce emissions, including those critical to the development of shale gas.

The U.S. has reduced its energy-related carbon dioxide output more than any other country, proving once again that when entrepreneurs and markets are free to invest in innovation, good things will happen.