In 2007, about 685,000 of a total of 19.2 million workers in the retail sector were involuntarily employed part time, according to the Bureau of Labor Statistics. By 2014, the number of involuntary part-time retail workers had more than doubled, to 1.4 million, even as the total number of retail workers declined to 18.9 million.

“Wages are just the first step in getting Walmart on the road toward being the type of employer that treats its employees with respect, and part of that is to set some standards around hours and work schedules,” said Rashad Robinson, executive director of ColorOfChange, an online civil rights organization that has campaigned for Walmart to raise wages and give workers better hours.

“It’s about creating an environment where employees are not just at the whim of Walmart,” he said.

At the heart of demands for higher wages and better hours, experts say, is the dwindling number of middle-class jobs. More primary wage earners who in the past may have held stable blue-collar jobs in manufacturing are now relying on low-wage jobs at Walmart or other discount retailers to support their families.

Mr. Rodriguez, who works at Walmart assembling bikes and other products, supports his fiancée on an income that can be as little as $900 a month. After spending about $550 on rent, $65 on gas for his car, as well as paying for food, diapers, cellphone costs and insurance, he can rarely afford new clothes or recreation, and when hours are especially scarce, he borrows money from his sister. He is looking for a second job to supplement his income, most likely a graveyard shift as a security guard. He is already $4,000 in debt.

“Walmart always provided jobs at the margins of the labor force — to people who were just re-entering the labor force after many years, for example, or supplementing a spouse’s income,” said Gary N. Chaison, professor of industrial relations at Clark University. “But what you’re increasingly finding is that it’s the primary wage earners who work at Walmart, because a lot of workers have more or less given up on getting middle-class jobs.”

“Now these workers are being pushed into Walmart-type jobs, they’re demanding higher wages, full-time jobs and better benefits,” he added. “So I wouldn’t necessarily interpret Walmart’s higher wage as a sign of an economic turnaround. I would interpret it as permanently bad news.”