U.S. officials acted this week to ease a nationwide shortage of baby formula. But none of the moves will create immediate relief for parents scrambling to find stocked shelves. And none fully address the underlying flaws of the more than $4 billion U.S. formula industry, in which business and government depend on one another to keep the country supplied.

Baby formula is one of the most tightly regulated food products in the country. That makes the barrier to new entrants high, and few brands have emerged as challengers to Similac and Enfamil, made by Abbott Laboratories and Reckitt Benckiser Group, respectively, since the two entered the market in the 1950s. Abbott and Reckitt were responsible for roughly 80% of infant and toddler formula sales in the U.S. last year, according to market-research firm Euromonitor.

Regulations also limit international brands from entering the U.S. from other countries.

The federal government is the product's biggest buyer, via the Women, Infants and Children supplemental nutrition program, which provides formula at no cost to families. The program's exclusive sales contract system ensures that in each state, one of the major formula brands has the majority of market share.

The result is a marketplace with little competition and little flexibility, making it vulnerable when something goes wrong.