It’s a mes­sage that has echoed from think tanks to politi­cians and lead­ing aca­d­e­mics and back to protest­ing work­ers in the street all week long. And bit by bit, the mes­sage is shap­ing pub­lic aware­ness that Amer­i­can work­ers earn­ing less than $15 an hour — a bit over two-fifths of the work­force — are gross­ly under­paid. Now this goal, ini­tial­ly seen as utopi­an but made prac­ti­cal large­ly by the Fight for $15 move­ment — is pro­duc­ing sig­nif­i­cant results.

“Your pay is too damn low,” pres­i­den­tial con­tender Bernie Sanders told union mem­bers who called in from around the coun­try to hear from him on Tues­day night.

In New York, the state labor com­mis­sion­er this week approved the rec­om­men­da­tion from a wage board, which had inves­ti­gat­ed New York City’s fast food indus­try, that its work­ers should be paid a min­i­mum of $15 an hour. Then on Thurs­day Gov. Andrew Cuo­mo — with Vice-Pres­i­dent Joseph Biden at his side — announced that he was launch­ing a cam­paign, main­ly direct­ed at Repub­li­cans con­trol­ling the state Sen­ate — to set the state min­i­mum wage for all work­ers at $15 an hour.

Maybe it’s not sur­pris­ing that Sanders, or even New York politi­cians (includ­ing those regard­ed as fair­ly con­ser­v­a­tive, like Cuo­mo), would back a $15 min­i­mum wage after that stan­dard was adopt­ed by Seat­tle, Los Ange­les, San Fran­cis­co and oth­er juris­dic­tions, but last week the Demo­c­ra­t­ic Nation­al Com­mit­tee also includ­ed a $15 min­i­mum wage in the pro­posed par­ty plat­form for next year.

On the same day as the lead­ing New York Democ­rats were announc­ing their plans, near­ly 100 pro­tes­tors gath­ered in the rain out­side Chicago’s City Hall demand­ing that Chica­go, which last year raised the min­i­mum wage over a peri­od of three years to $13, catch up with New York and adopt $15 as the min­i­mum for all work­ers. Although fast food work­ers led the Chica­go protest, many oth­er groups of work­ers have joined in the Fight for 15: home care work­ers, child care work­ers, and nurs­ing home work­ers who are fight­ing for $15. (Some have union con­tracts but at wage lev­els part­ly depressed by the low min­i­mum wage.) Con­stituen­cies for the cam­paign con­tin­ue to grow, increas­ing its strength.

But in many parts of New York, work­ers will need a min­i­mum of $21 – 22 an hour by 2021, accord­ing to cal­cu­la­tions using data from the Eonom­ic Pol­i­cy Insti­tute. The gap between the min­i­mum wage – $7.25 by fed­er­al statutes, $8.75 in New York state — and either $15 or $22 is enor­mous. It is part­ly filled by tax­es that are not suf­fi­cient­ly pro­gres­sive to sup­port $13 bil­lion a year in pub­lic assis­tance to very low-paid workers.

Work­ers’ pay has fall­en below appro­pri­ate lev­els for all work­ers, not only because of pol­i­cy fail­ures, such as not rais­ing the min­i­mum wage, but more gen­er­al­ly because work­ers’ com­pen­sa­tion has not kept up with pro­duc­tiv­i­ty growth from 1973 to the present, as it had from 1948 to 1973, the ​“gold­en age” of Amer­i­can cap­i­tal­ism. At the time of the shift, the U.S. econ­o­my was begin­ning to feel pres­sures from its increas­ing inte­gra­tion into a glob­al econ­o­my that was less con­trolled by lead­ing gov­ern­ments. Cor­po­ra­tions were com­plain­ing of a squeeze on their prof­its. And big busi­ness­es were orga­niz­ing them­selves more as a uni­fied force, not just as spe­cif­ic indus­tries, to increase their polit­i­cal influ­ence and to fight unions, con­sumer advo­cates (like Ralph Nad­er), pro­po­nents of full employ­ment eco­nom­ic poli­cies, and the emerg­ing environmentalists.

Accord­ing to a new paper by Josh Bivens and Lawrence Mishel from the Eco­nom­ic Pol­i­cy Insti­tute, wages did not stag­nate because pro­duc­tiv­i­ty growth slowed (although busi­ness-backed poli­cies often did slow pro­duc­tiv­i­ty growth). Rather, more of wages and salaries went to the cor­po­rate elite, and more of income went to own­ers of cap­i­tal rather than to work­ers (and, of course, CEOs ben­e­fit­ted from both trends).

More pre­cise­ly, from 1973 to 2014 net pro­duc­tiv­i­ty grew by 72.2 per­cent, but ​“infla­tion-adjust­ed hourly com­pen­sa­tion of the medi­an work­er rose just 8.7 per­cent.” Ris­ing inequal­i­ty accounts for more than two-thirds of the gap between pay and pro­duc­tiv­i­ty. And, Bivens notes, just since 2000, the decline in labor’s wage share of cor­po­rate income has cost work­ers $535 bil­lion. (If this mon­ey were shared among all work­ers even­ly, every work­ing Amer­i­can would get a raise of $3,770.)

Many dif­fer­ent strate­gies com­bine to cre­ate the inequal­i­ty gap between the top exec­u­tives and own­ers of cap­i­tal and work­ers. One set of strate­gies involves play­ing off wage and rights dif­fer­en­tials in the glob­al econ­o­my. Anoth­er set, cre­at­ing ​“the fis­sured work­place,” to use the term coined by cur­rent Labor Depart­ment Wage and Hour Admin­is­tra­tor David Weil, min­i­mizes the respon­si­bil­i­ty of employ­ers and shifts risk to workers.

Last week the Nation­al Employ­ment Law Cen­ter exam­ined the ​“on-demand” econ­o­my, epit­o­mized by Uber taxi ser­vice but includ­ing a grow­ing num­ber of oth­er busi­ness­es. Although these firms claim to be inno­v­a­tive, the NELP report found them for all prac­ti­cal pur­pos­es to be much like old-fash­ioned ​“labor bro­kers,” dis­patch­ing work­ers — who are real­ly their employ­ees, not inde­pen­dent con­trac­tors — to pro­vide ser­vices for indi­vid­u­als or businesses.

Now most of these ​“on-demand” work­ers lose out on the pro­tec­tions work­ers are pro­vid­ed by law. NELP, for exam­ple, found that they should — but typ­i­cal­ly do not — receive guar­an­tees of min­i­mum wages, right to orga­nize, or social insur­ance pro­grams (such as social secu­ri­ty, Medicare, work­ers’ com­pen­sa­tion and unem­ploy­ment insur­ance). The lack of these rights also ends up depriv­ing them of income that goes to their boss­es and the com­pa­ny investors.

The decline of unions has been a major cause of this grow­ing inequal­i­ty, but accord­ing to new research by Har­vard Uni­ver­si­ty pro­fes­sor Richard Free­man and David Mad­land of the Cen­ter for Amer­i­can Progress, the den­si­ty of union mem­ber­ship in a neigh­bor­hood is one of the most impor­tant deter­mi­nants of the degree of eco­nom­ic mobil­i­ty of poor chil­dren (at least as impor­tant, for exam­ple, as school drop-out rates). Thus the decline of union­ism helps to explain why not only has inequal­i­ty increased but oppor­tu­ni­ty to move up has decreased in the Unit­ed States.

For most work­ers, the prob­lem is not only that their pay is too damn low. It’s also that they have no col­lec­tive pow­er and voice to do any­thing about it. That hurts them, their chil­dren and the whole coun­try, but it feeds the billionaires.