Cory Booker is a US senator from New Jersey and Democratic candidate for president. The opinions expressed in this commentary are his own.

On December 4, 1889, US Senator John Sherman of Ohio introduced the Sherman Antitrust Act into the 51st Congress of the United States. Three months later, he took to the Senate floor to defend his proposal, which would eventually become law, and form the linchpin of the American antitrust system.

Of all the problems upending the social and economic order of the United States, he said, "none is more threatening than the inequality of condition, of wealth and opportunity that has grown within a single generation out of the concentration of capital into vast combinations to control production and trade and to break down competition."

Sherman's words were spoken 129 years ago, but they would fit seamlessly into today's political and economic reality, where fair and open markets have been replaced by just a few giant corporations in sector after sector of our modern economy.

Nowhere is this more clear than in our agriculture sector and food system. Four companies — Archer Daniels Midland (ADM), Bunge, Cargill and Louis Dreyfus — control as much as 90% of the global grain market, and three companies — Bayer-Monsanto, Corteva Agriscience, ChemChina-Syngenta — now control over 60% of the world's commodity crop seeds. In the past three decades, the top four steer and heifer packers in our country have expanded their market share to 85%.

These excessive levels of concentration and market power are devastating our independent family farmers and ranchers and hollowing out the rural communities in which they live. Farmers and ranchers are being forced to sell into even more concentrated marketplaces that unfairly reduce the prices they receive for their crops and livestock, and unfairly increase the cost of labor, machinery, livestock, seeds and chemicals.