President Joe Biden’s strategy of bolstering labor unions as a way to enhance American workers’ pay is running up against a half century of setbacks for organizing workers.

In a high-profile move last week, Amazon.com Inc. workers at a Bessemer, Alabama, warehouse voted against joining a retail union, despite a pro-labor video message to the distribution workers from Biden.

Labor union membership has slumped to 10.8% of wage-and-salary employees in 2020 from almost a third of workers in 1960. The globalization of supply chains, technological advancements that allow companies to replace labor, legal barriers to organizing and the shrinking share of factory workers -- traditionally easier to organize -- in the workforce have all taken a toll.

Creating “good-paying, union jobs” is a centerpiece of Biden’s $2.25 trillion infrastructure-focused economic plan, which also calls for new laws to encourage unions. “Even in the face of automation and globalization, America can and must retain well-paid union jobs and create more of them all across the country,” according to a White House summary.

Wage growth was relatively subdued for most of the 2010s expansion. With unemployment still elevated in the wake of the pandemic, boosting productivity and generating a tight labor market may provide a more viable path to raising pay than unionizing.

“It will be very hard to resuscitate unions and collective bargaining in their current form,” said Harry Holzer, a Georgetown University professor and former U.S. Labor Department chief economist during the Clinton administration. “While I am sympathetic to strengthening unions, I am very pessimistic.”

Biden is pushing to pass the Protecting the Right to Organize (PRO) bill, which is intended to boost union membership after decades of decline. While the House approved the measure in March, it faces long odds in the Senate, where it will need the support of at least 10 Republicans.