Almost immediately, I was barraged by much of lefty Twitter with a huge ratio. A few people tried to genuinely debate me, explaining that unions could be good for even workers who feel they are well off. But it was mostly insult after insult, and after a while, I stopped looking at my notifications.

A year and a half later, sleepless but amped up on coffee and solidarity from a 29-hour marathon final bargaining session, I celebrated with the rest of the bargaining committee, made up of select union members who negotiated directly with the company, as the union and Vox Media management reached a contract agreement.

I had done a complete 180 on unions.

Good organizing and outreach from colleagues helped change my mind about the need for a union at Vox Media specifically. But so did approaching the research on unions the same way I would any topic in my reporting: by looking at the data and talking to experts.

Research suggests that unions have their biggest effects from density. When more people are part of a union, unions don’t just boost their workers’ wages and benefits; they also lift up those they don’t represent.

Unions accomplish this in two ways: The first is through bargaining on wages and benefits, which, because unions tend to represent lower- and middle-class workers, helps people who generally haven’t gained as much from the US economy in recent decades. Second, politically active unions push for progressive policies that lift up the entire working and middle classes, not just their members. Indeed, unions were crucial to some of the biggest gains in this area in the past century, from the New Deal to the Affordable Care Act.

In doing this, unions also help address income and wealth inequality, which have fueled social and political discord in the US in recent decades. Based on reviews of the research, the decline in unions— of about 66 percent since the 1940s and ’50s — can explain about 10 to 30 percent of the rise in inequality we’ve seen in the past several decades.