The meat processing industry in the United States has become more concentrated over the years, with the four largest companies processing 67% of the country's pigs in 2019 compared to 34% in 1980. The increase in concentration has been driven by the construction and expansion of facilities by large processors rather than mergers between competing companies. Additionally, there has been a shift in how pigs are produced and sold, with most pigs now being raised under production contracts with integrators rather than sold on the spot market.