With unemployment rates at record lows, the number of people who have gone on strike in the U.S. has soared.

The number of striking workers ballooned to nearly 500,000 in 2018, up from about 25,000 in 2017, according to the Bureau of Labor Statistics. This is the largest number of people who have walked out on work since the mid-1980s.

As employment numbers have rapidly risen over the 10-year expansion, wages have struggled to keep up. And as the labor market tightens, workers are becoming more confident about striking for better salaries and benefits.

In September, workers for General Motors walked out in what has now become the company's longest strike in decades. The strike began after the auto manufacturer could not reach a contract agreement with labor union United Auto Workers. The walkout is estimated to have cost General Motors upwards of $2 billion, according to Bank of America.

Not only are people striking, but the number of people who have voluntarily quit their job, which can be viewed as a measure of job market confidence, hit an all-time high in July. The percentage of striking workers in the total workforce is currently at about 0.3%, compared with 0.4% in the mid-1980s.

Workers are feeling left behind in the expansion. As the gap between executive salaries and worker pay expands, more people are becoming discontent. In the recovery, corporate profits stabilized long before household income, acting as a spark for the surge in strikes, according to The New York Times, which was the first to report on this data.

General Motors workers aren't the only ones walking out on the job. About 3,500 Mack Truck employees, who are also UAW members, are currently striking across three states for the first time in 35 years over their contracts. The union is seeking better contract terms on issues ranging from wage increases and holiday schedules to health care coverage and retirement benefits.

Among other notable actions, Chicago public school teachers are in their third day of a strike, demanding higher salaries, better benefits and more resources for the classroom. The strike has effectively canceled classes for approximately 361,000 students.

Leading up to the 2020 presidential election, worker pay and employee benefits have been a central campaign point for a growing number of politicians, including Sens. Elizabeth Warren, D-Mass., and Bernie Sanders, I-Vt. In August, CEOs from nearly 200 companies said shareholders should no longer be the main focus of businesses and that companies should be focusing more on investing in stakeholders such as employees and customers.