(FORTUNE Magazine) – Do economic sanctions work? Not against South Africa, says President Reagan, so he will probably veto a bill Congress has sent him that would impose sanctions -- mainly bans on certain imports and new direct investment -- on the country. But the House and Senate seem likely to override the veto and make the sanctions law. If that happens, it will mark at least the 50th time since 1960 that the U.S. has used sanctions as a foreign policy tool. No other nation has used them nearly as often. While economic sanctions have sometimes worked, this time it looks as if Reagan is right. The record of recent sanctions is not encouraging, as the table shows; it is based on data from Economic Sanctions Reconsidered, a book by Gary Clyde Hufbauer and Jeffrey Schott, economists at the Institute for International Economics in Washington. Actions against large and powerful nations like the Soviet Union have proved fruitless, and nations such as Cuba and Nicaragua have weathered the wrath of the U.S. mainly through Soviet support. Libya's oil has shielded it from economic sanctions. Trade bans are most effective when applied to an economically fragile country with sparse internal resources and little outside support. Congress's South Africa bill is not strong enough to achieve its goal: pressuring the regime of P. W. Botha to dismantle apartheid and open negotiations with black leaders. While South Africa lacks a major benefactor, it has ample economic and military resources to survive on its own, if necessary. Chances are that nothing short of watertight economic sanctions strictly observed by the U.S., Japan, and the European Community would be effective. The long history of sanctions has never seen such orchestrated, powerful action.

CHART: HOW U.S. SANCTIONS HAVE FARED CUBA 1960 to present OBJECT: Total trade ban to undermine Castro regime, dis courage it from f reign military adventures. RESULT: Failure. Cuba gets Soviet aid, sends troops abroad. KAMPUCHEA(Cambodia) 1975 to 1979 OBJECT: Total trade ban to improve human rights. RESULT: Failure. Pol Pot regime had no wish to trade with U.S. and received aid f om China. UGANDA 1978 to 1979 OBJECT: Total trade ban to improve human rights, undermine Amin regime. RESULT: Partial success. Contributed to worsening situation that led to Amin's 1979 overt row. U.S.S.R. 1980 to 1981 OBJECT: Ban on grain exports to retaliate for invasion of Afghanistan. . RESULT: Failure. Other countries increased grain sales to U.S.S.R. LIBYA 1982 to present OBJECT: Ban on imports of Libyan oil to undermine Qaddafi regime, end its support of terrorism. RESULT: Failure -- so far. Though oil revenues were hurt, U.S.S.R. continues to provide mil tary aid. NICARAGUA 1985 to present OBJECT: Total trade ban to undermine Sandinista regime, protest support f rebels in El Salvador. RESULT: Failure -- so far. U.S.S.R. has offered $500 million in aid.