During the early years of exodus, the number of departures depended largely on the status of the United States-Soviet relationship and on financial pragmatism. In hopes of achieving economic benefits from the US, the Soviet government sporadically opened its emigration gates, sometimes even in contradiction of its own legislation. Thus, despite the "Diploma Tax" that was instituted in December 1972 and required exiting Jews to pay for the higher education they received in the USSR, the government allowed two groups of 900 persons each to leave shortly thereafter without paying. By March 1973, the tax was revoked in the face of extreme pressure from the international public community and the Soviets' fear of not being awarded Most Favored Nation status by the U.S. In December 1973, the Jackson-Vanik Amendment, which linked trade agreements with the USSR to freedom of its citizens to emigrate, was passed in the U.S. Congress by a landslide. This legislation was an indicator of the degree to which the Soviet Jewry struggle had won the moral support of the West and had spurred the American Jewish community into action. The Soviet authorities were now subject to criticism not only from scattered groups of dissidents and refuseniks, but from tens of thousands protesting in front of Soviet embassies and consulates around the globe. Over time, these combined factors impacted the numbers of the Jews leaving the Soviet Union.