It's a simple lesson from Economics 101: reduce demand for a product and fewer people will buy it. The legalization of marijuana in 24 states and Washington, D.C. has helped reduce the amount of drugs being smuggled into the U.S. from Mexico, data shows.

Donald Trump missed the memo. During the second presidential debate on Sunday when, Trump said more drugs are being smuggled into the U.S. through the U.S.-Mexico border along California, New Mexico, Arizona and Texas.

"We're also letting drugs pour through our southern border at a record clip. At a record clip. And it shouldn't be allowed to happen," Trump said during the debate.

Christopher Ingraham, a journalist for the Washington Post, fact-checked Trump and found that the data from the U.S. Customs and Border Protection on drug seizures doesn't backup his claims that a "record" amount of drugs are being smuggled across the border. Ingraham compared the U.S. Customs and Border Protection report on drug seizures from 2011 with the report for 2015 and found that the amount of drugs seized by authorities at the border decreased dramatically in the last five years.

In 2011, the authorities seized approximately 2.5 million pounds of drugs along the border in California, Arizona, New Mexico and Texas. In 2015, the total weight of drugs seized dropped to 1.5 million pounds.

As marijuana laws are reformed across the U.S., users can now get better quality marijuana from stores at similar prices compared to a lower quality product from Mexico. While the dramatic decrease in the total weight of drugs seized at the border is primarily due to the fact that marijuana seizures are down and the plant is bulkier and heavier than more concentrated forms of drugs like cocaine, heroin and methamphetamine, the data shows drops in seizures for most of those drugs too.

The amount of cocaine seized fell by half, from 8,763 pounds in 2011 to 4,294 pounds in 2015. The amount of heroin seized is up this year, 515 pounds in 2015, from 2011, 387 pounds, but down compared to the last two years: authorities seized 559 pounds in 2013 and 575 pounds in 2014.

Trump's claim that drugs are coming over the border in a "record clip" is true for one drug: methamphetamine. The amount of meth seized by U.S. Customs and Border Protection officers went up threefold from 2011 to 2015, reaching 6,429 pounds seized in 2015 from 1,838 pounds five years ago.