In one much-discussed paper presented at Sintra, Uta Schönberg, a professor at University College London, compared data from Germany and France and came to the conclusion that low wage growth and rising inequality were a result of diminished bargaining power by workers.

Flat wage growth in Germany during the last two decades coincided with reforms that allowed companies to opt out of collective bargaining agreements, weakening union power. In France, where union agreements applied to whole industries and were binding for companies, wages continued to climb and inequality was less pronounced.

But France paid a price. While unemployment fell below 4 percent in Germany, it remains above 9 percent in France. The implication is that companies may not hire as much if they are locked into union wage contracts.

Professor Schönberg pointed out that pay in Germany has begun rising again, suggesting that the effect of reforms was temporary. At a certain point, low unemployment does still seem to lead to higher wages. It just may take longer than it used to.

That is no doubt what the European Central Bank is counting on. Wages are a key issue for the bank because, by law, its job is to keep inflation at or close to 2 percent. It would be hard to believe that inflation is on an upward trend without an accompanying rise in pay.

Even after five years of steady economic growth, until recently inflation in the 19-nation euro area remained stubbornly below the official target. Consumer prices rose at an annual rate of 1.9 percent in May and 2 percent in June, but the numbers were not very convincing. The increases were due almost exclusively to a steep rise in energy prices, which fluctuate often.

Wage growth “was the key variable we would look at for convergence of inflation,” Mr. Draghi said at a news conference in June after a meeting of the European Central Bank’s Governing Council.