The International Longshoremen’s Association launched a major strike on Tuesday that saw 45,000 workers shut down ports across the U.S.’s East and Gulf coasts indefinitely

Unions representing auto workers, actors, hotel housekeepers, and aircraft-assembly workers all called strikes as organized labor made itself heard over the past year. The U.S. dockworkers who went on strike early Tuesday are just the latest unionized group to back their demands for better contracts by walking off the job to illustrate their value to both the national economy and their employers’ bottom line.

If not resolved soon, the strike could eventually affect the shipping of 40% to 50% of U.S. imports, S&P Global Market Intelligence writes.

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