In "NAFTA did more harm than good for Mexico" (Dec. 8), Richard Patten relies on many common misconceptions about the landmark trade agreement to make his point. It's essential that we clear these up in order to understand the true benefits of agreements such as NAFTA and new agreements that are being negotiated.

Patten implies that somehow both countries have been losers as a result of NAFTA, claiming damages to jobs and livelihoods in the United States and in Mexico. His assertion could not be further from the truth. Both countries have benefited enormously in the two decades since the agreement was enacted, as each has found a neighbor more empowered to purchase its goods and services.

Today, Mexico is the second-largest purchaser of U.S. goods and services after Canada, buying more of what U.S. workers produce than China and Japan combined, and nearly as much as the entire European Union. There is also a feedback effect to this, as many of the finished goods we buy from Mexico are made from raw materials originally produced here in the United States.

Mexico has unquestionably benefited as well. Annual trade with the United States has grown from $120 billion in 1995 to $480 billion last year, accounting for the bulk of Mexico's trade growth in that time frame. According to Mexico-based research firm GEA, products are more affordable for Mexican consumers, with the cost of basic household goods in the country cut in half since NAFTA was put into force. Yale economist Lorenzo Caliendo makes the argument that cross-border trade has caused real wages to increase in Mexico during the NAFTA era.

This is certainly not to say that Mexican society is free of social and economic challenges. But trade has been an unquestionable boon in confronting those problems, rather than a force to exacerbate them, as Patten suggests. The Mexican government recognizes NAFTA's merits. It's why Mexico now has more regional trade agreements in place than the United States, and why the government is enthusiastically pursuing the Trans-Pacific Partnership alongside 11 other nations, even as it charts an ambitious domestic reform agenda, as well.

It's clear that agreements like the Trans-Pacific Partnership and others have the potential to make food more affordable and more environmentally friendly by allowing each partner nation to grow the agricultural products best suited to its climate and soil, and then trade with others using a consistent set of standards.

Again, trade between the United States and Mexico offers a powerful example. Although agricultural trade between the two countries was nearly equivalent in 2013 ($18.9 billion of U.S. goods went south; $18.4 billion of Mexican goods went north), it's the type of food moving that matters.

Yes, as Patten asserts, more U.S. corn has flowed into Mexico under NAFTA, but this is almost exclusively yellow corn, which is used as animal feed there; it helps raise animal protein like chicken that Mexican consumers can now increasingly afford. Mexico continues to be a strong producer of white corn, which is the predominant corn that people eat in that country, usually in the form of tortillas.

Cargill is a strong supporter of trade agreements, which create jobs, expand economies, and help to raise standards of living and nutrition. NAFTA is a shining example of the benefits of free trade, and one we should keep in mind as we consider how to move forward as a nation. The United States can either sit on the sidelines while other countries sign on to beneficial agreements such as the Trans-Pacific Partnership, or we can choose to participate to secure a growing and prosperous future for our country.

Greg Page is executive chairman of Cargill.