American supermarket employees (especially in California and Illinois by personal observations) would kill to negotiate contracts on a sector-wide basis.
The streamlined version of sector-wide labor agreements -- the French/French-Canadian practice requiring non-union firms to operate under agreements worked out by unionized firms -- is ready and waiting for America's seamless transition to a fair and balanced labor marketplace. Economies from South America to South East Asia use mixes of mostly unionized to mostly non-unionized sector-wide rules -- some confined to certain industries (sector - sector-wide) -- there's all ways to do it.
Adopting French-blueprint sector-wide here would not require -- on the run -- building a broader union base than we ever built before (as going German style, full-out unionized could). And, the French-Canadian example will always be right next store for our convenient perusal -- in an economy we can reasonably fathom.
PS. Sector-wide collective bargaining was put in place by after WWII industrialists in Europe -- not labor unions -- to keep unions from going on a race to the top. Turns out to stop the race to the bottom just as well. Wal-Mart closed 88 big boxes in Germany because it could not compete pay the same wages and benefits as everyone else. Now in practice around the world -- as far flung as Argentina and even Indonesia.
Average income actually doubled since -- as real world 1968-Americans might have anticipated. 2007-working Americans -- if and when somebody troubles to fill them in on their missed prosperity (50 to 90 percentile incomes could mostly have done significantly better; 25 to 50 percentile incomes mostly held plus a little) -- will have one culprit to mostly contemplate: the race of under-powered (ultimately because under-informed?) labor to the bottom.
[ * 12.5% of American incomes are officially reported below today's, decades irrelevant, federal poverty standard: three times the price of the cheapest emergency diet -- dried beans only please, no canned! -- try the 2002 book Raise the Floor for realistic poverty parameters. ]