The decline of private-sector unions in America--how much is because of weak labor laws, and how much is because of the way the economy is changing?

A lot of people don't realize that  the decline has occurred all over the advanced capitalist world, even in countries with laws that protect and promote unions far more than in the U.S. Essentially, we have seen a great shrinking in the advanced world of what was the core union demographic: manufacturing and mining workers. Production in those sectors is high, but companies need fewer workers to do it--and they've transferred much of the work to developing countries like China, where they can get away with much lower wages.

But, yes, the United States is a special case. The peak of union density in the US following the Second World War was lower than in other wealthy democracies, and its trough is now lower, too (France actually has smaller percentage of union members than the US, but union contracts cover almost the entire workforce.). In no other advanced country is the entire political economy as relentlessly opposed to unionization as it is here. The U.S. has the most hostile anti-union management/ownership class, and corresponding conservative politicians and media to assist it, in the advanced world.  The legal framework assumes that companies--the people who sign workers check--have a right to interfere with their right to choose a collective bargaining agent. Workers do not get a corresponding right in the United States to participate with management in investment decisions. Anti-union activity is flourishing billion dollar consulting business. Laws to fight it are toothless. Today, decades after the National Labor Relations Act became law, Republicans don't accept its basic legitimacy--and do everything they can to undermine the NLRB.

And it's not like that elsewhere?

Pretty much in every other country in Western Europe, Canada, even Australia and the U.K. (which share some labor-management features with the U.S.), the assumption is that unions are basic ingredient of liberal capitalism. Among conservatives and business owners in those countries, you'll hear a lot about how they are inefficient, too powerful, or just pains in the ass. But pretty much everybody accepts them as a normal part of the political/economic/legal landscape. That's simply not the case here.

What's ironic about that is that unions are inherently conservative institutions, which historically developed parallel with the development of capitalism itself. They are as much a part of capitalism as Henry Ford or Apple. Unions use contracts--and there's nothing more intrinsic to capitalism than the right of contract--to link their members to the fortunes of the companies they contract with. They are capable of having huge fights with capital (as in the thirties)--which raise the hopes of leftists--but, usually, over the attainment of very incremental ends---which disappoint leftists. Marx had nothing but contempt for British trade unionists, and Trotsky saw no value in unions at all.  Yet conservatives and most libertarians hate them. Weird.