Kevin already did important yeoman's work pointing out some of the simple factual inaccuracies riddling Russell Roberts' anti-union screed, but it's worth noting what a conceptual mess the article is. Roberts writes, "When more than 90% of the private-sector labor force isn't unionized, why do 97% of us earn above the minimum wage? If our bargaining power is so pitiful, why don't greedy employers exploit us and drive wages down to the legal minimum?"
This seems like a discussion question at the end of an Introduction to Economics textbook chapter. And Roberts' answer is about as illuminating. Meanwhile, the issue with unions is, in the immortal words of Samuel Gompers, "more." Just because the median laborer is clearing $5.15 doesn't mean he's making as much he theoretically could. Distribution matters. Unions get more for their workers, a "more" that would otherwise fall into executive pockets and corporate profits. The question isn't whether they save us from economic dystopia, but whether they make the economy better for the median participant.
Indeed, Roberts' final conclusion eviscerates his point. "A better way to increase wages [than unions]," he writes, "is to make workers more productive. That lifts everyone's standard of living." At least it did. In the post-war era, worker salaries tracked productivity increases rather precisely. This was also the high period of union density in America. Post-1979 or so, that link shattered. "Coincidentally," this is around when Reagan and his merry band of plutocrats effectively legalized and encouraged unionbusting. In the past few decades, economists have shown that productivity increases are going almost entirely to the top tenth, while median incomes stagnate or retreat. Without unions and robust worker bargaining power, those magic productivity increases haven't been doing much for workers. But Roberts, of course, doesn't tell you that.
Also at Tapped