Here’s an important detail about the strength of our domestic oil industry that is often lost in the larger debate over opening more of the country to drilling and exploration: Yields are up at many existing oil fields.

The American Petroleum Institute reported this week that U.S. crude oil production reached a four-year high in October, due largely to the success of advanced drilling technologies that have helped improve yields in deep waters in the Gulf of Mexico and elsewhere.

It’s a milestone that is important for a number of reasons. It shows that the oil sector is inventive and enterprising, constantly adopting new techniques that will improve on the existing way of doing business.

These high yields, mind you, are coming from some not-so-young properties, at a time when critics maintain that oil is past its prime, and past its peak. And they beg the question, if oil producers can increase yields from existing properties, what might they be able to achieve on a spanking new field in one of the disputed sites around the country?

The 5.36 million barrels of crude oil per day that were produced during the month of October offer strong evidence in favor of additional drilling around the country. It’s a strong level of production that suggests that additional exploration has a high likelihood of success, and also that the producers overseeing the drilling would make the most of each project, just like they are doing at older fields. It flies in the face of the notion that the oil industry favors drilling with abandon, or only wants to break ground on new sites because all of the older ones have dried up. Rather, it reflects a long-term commitment to each and every project.

The debates over new drilling around the country may take a long time to resolve. But it’s nice to know that oil producers are keeping busy while they wait.