The U.S. has reopened a border crossing in Arizona to cattle from Mexico as part of a broader effort by the Trump administration to reduce near-record-high beef prices. But economists doubt the move will mean much to prices shoppers see at grocery stores. The U.S. Department of Agriculture has said concerns about the New World screwworm’s spread lessened enough to allow Mexican cattle to cross the border at Douglas, Arizona, starting Monday. While Mexico has traditionally exported 1.1 million head of cattle a year to the U.S., economists say the biggest problem is that the U.S. cattle herd is the smallest in 75 years.