Over 1,500 McDonald’s employees and supporters protested at the company’s headquarters in Oak Brook, Illinois, on May 20, a day before the annual shareholder meeting.

They are demanding a $15 minimum wage for fast-food workers.

Larger protests are planned for May 21, before the company’s annual shareholder meeting.

McDonald’s has been under pressure from workers to raise wages, just as investors have become increasingly unhappy with the company’s slumping sales.

In the same time, customers in the company’s biggest market – the US, which is responsible for 40% of its operating income – have been increasingly foregoing McDonald’s and other fast-food restaurants in favor of so-called “fast casual” chains like Shake Shack and Chipotle.

That has caused McDonald’s share price to sink – and let to grumbling amongst shareholders.

McDonald’s has banned media from attending the management meeting on May 21.

Photo Reuters

Earlier in May, CEO Steve Easterbrook – who took over the company in January – unveiled plans to turn around the company after it reported yet another quarter of disappointing results.

McDonald’s has been under pressure for over two years by the Fast for 15 campaign, a group of workers, backed by traditional labor unions. They have called on McDonald’s and others to raise the base amount it pays workers to a so-called “living wage” of $15 per hour.

The current US federal minimum wage is $7.25, but some states and cities – most notably, Los Angeles – have higher minimums.

Outside McDonald’s headquarters in Oak Brook, protesters carried banners and balloons, and chanted slogans.

However, McDonald’s has already said it plans to raise the wage it pays workers to above $9 per hour – and several other companies, including Wal-Mart and Target, have said they will increase their hourly minimums in the wake of the protests.

Part of the move, experts say, is that as the US economy recovers, large companies have to increase their base wages to keep workers.

But the companies also face mandatory wage increases in the several states and US cities that have voted to raise the local minimum wages since 2014.

On May 19, Los Angeles became the largest US city to boost wages, voting to increase the minimum wage in the city to $15 per hour by 2020. Experts say that amounts a $2.4 billion wage increase to over 500,000 workers in the city.