It was the Champagne pop heard across the economy. One year ago Saturday, a fired Amazon warehouse worker turned labor activist sprayed Champagne and then drank from the bottle outside federal labor offices in New York City.

Swarmed by supporters and media, Chris Smalls toasted a victory: the first Amazon union in the U.S., led by Smalls and other workers at an 8,300-person warehouse on Staten Island, a feat few believed they could pull off.

A hollow victory?

Since then, though, the Amazon Labor Union has gained little ground. It has yet to win another union election. And Amazon still refuses to sit down for contract negotiations.

In fact, despite the buzz around what seemed like a labor resurgence — the historic win at Amazon, as well as spirited campaigns at Starbucks, on college campuses and retail stores across the country — the overall picture for unions remains bleak.

This week, we got a window into why. On Wednesday, fresh from his third stint as Starbucks CEO and under threat of subpoena, Howard Schultz testified on Capitol Hill about the aggressive steps he's taken to discourage unions at Starbucks. Despite findings by federal labor officials that Starbucks has violated labor law on numerous occasions, Schultz repeatedly denied wrongdoing.

"Let me say under oath: These are allegations, and Starbucks has not broken the law," Schultz told the Senate Committee on Health, Education, Labor and Pensions.

Union membership is stalled

Just 10% of American workers belonged to a union in 2022, the lowest in Labor Department records going back to 1983, when the rate was 20%.

Never mind that 71% of Americans approve of unions, the highest in nearly six decades and up from 48% in 2009, a Gallup poll conducted last summer found.

The bottom line is that labor law itself is tilted in favor of employers, say researchers who study labor movements, often making corporate hostility toward unions too hard to overcome. The recent groundswell of public support is far from enough to spark a union comeback.

"Those of us who have been watching this stuff for many decades have actually been pleasantly surprised by the success that has occurred, but it's too modest in scope and too fiercely resisted by employers" to move the needle, says Ruth Milkman, a labor sociologist at the Graduate Center at the City University of New York.

One way to thwart a union: delay, delay, delay

A big part of the problem, Milkman says, is that under current labor law, companies can slow down every stage of the organizing process. And the longer it takes to organize a union, the more likely it is that workers will give up.

Starbucks, for example, insisted early on that individual stores, which often employ just 25 to 30 people, should not be allowed to hold union elections, but rather, all stores in a geographic region must vote together in one election, increasing the degree of difficulty for union organizers. Federal labor officials ruled against Starbucks, and elections proceeded at the store level, but not without significant delays.

Fast forward more than a year. Close to 300 Starbucks stores have now unionized, but not a single one has negotiated a contract. Starbucks and Workers United blame each other for refusing to bargain in good faith, but the union has more to lose. Organizers say it's harder to convince coworkers to vote for a union when they can't show what they'll gain from union membership.

Meanwhile, collective bargaining at the Amazon warehouse on Staten Island has yet to begin, due to a parade of objections and appeals filed by Amazon over the past year.

Following a lengthy Zoom hearing last summer to consider the company's objections to the election, federal labor officials found the complaints meritless and in January ordered the company to begin negotiations with the union.

But Amazon has since formally requested a review of that decision. If that review doesn't go in its favor, Amazon can still take its case to federal court for another round.

The cost of doing business

Unions have fought back, filing hundreds of unfair labor practice charges over anti-union activities, citing things like companies closing stores, cutting hours, threatening and firing organizers, and failing to bargain in good faith. (Companies have also filed unfair labor practice charges against unions, but far fewer.)

But even where the NLRB has found violations of workers' rights to organize, the board's decisions don't have much financial bite. The agency's administrative law judges can only impose what are called "make whole" remedies, things like back pay, reinstatement and reimbursement for financial harms suffered as a result of unlawful activities.

"It's a cost of doing business," AFL-CIO President Liz Shuler said in Senate testimony earlier this month. "Right now, you actually get a bigger fine for violating fishing laws in many states than you do for busting unions."

A push for tougher penalties

President Biden and Democratic lawmakers have pushed for passage of the Protecting the Right to Organize Act, known as the PRO Act, to fix some of the weaknesses of current labor law, starting with civil penalties of up to $50,000 for violating workers' rights.

But with a divided Congress, hopes for passage are slim. And without any change in the law, Milkman says it's hard to imagine a significant uptick in the unionization rate in the U.S.

With the PRO Act going nowhere, Sen. Bernie Sanders is turning to public shaming of those in power.

"Enough is enough. Amazon must come to the table and negotiate a fair contract with workers NOW," Sanders tweeted in January, after labor officials ordered Amazon to begin collective bargaining.

And in opening remarks to Schultz's hearing, he called out Starbucks for waging "the most aggressive and illegal union-busting campaign in the modern history of our country."

A public shaming, but will it lead to progress?

It's unclear, though, how much can be gained through words alone.

On Wednesday, Sanders was unable to elicit a promise from Schultz that Starbucks would exchange contract proposals with the union within 14 days. He failed to get Schultz to admit to any missteps in his handling of the union campaign.

Instead, Schultz did what he's done proudly for decades, outlining the competitive wages and industry-leading benefits that Starbucks affords workers, including free college tuition and company stock, even for part-time employees.

There is growing outside pressure for Starbucks and its new CEO Laxman Narasimhan to reconsider the company's anti-union stance. At a meeting last week, shareholders voted to approve a proposal, brought by heavyweight investors including New York City's pension fund, for an independent assessment of Starbucks' labor practices — an examination of its adherence to commitments it made to uphold workers' rights.

Still, it's unclear what that vote may mean. The shareholder proposals are not binding, and in encouraging a no vote on the proposal, Starbucks said it had already begun its own third-party human rights impact assessment.

Editor's note: Amazon is among NPR's financial supporters and pays to distribute some of our content.