Among the overlapping categories that you listed, the only sector that's relatively well organized in America are government employees. According to the BLS, "About 36 percent of government workers were union members in 2004, compared with about 8 percent of workers in private-sector industries" (at <http://www.bls.gov/ news.release/union2.nr0.htm>). That is a huge gap. When the only stronghold of organized labor becomes workers whose wages and benefits directly depend on tax dollars, which in turn depend on profits produced by the work of unorganized workers, organized labor has a big political and economic problem at hand
^^^^^^ CB; For this reason, privatization in the U.S. is especially union busting.