Algerians re-elected Chadli Bendjedid to his third presidential term by a smaller margin than ever before, but still gave him a mandate to continue reforms that began two months ago. Thg Interior Ministry announced early today that Bendjedid, the single candidate, had captured 81 percent of Thursday's vote. About 89 percent of the country's 12 million eligible voters cast ballots. Voter turnout in Algeria traditionally runs at about 90 percent. As in most one-party states where a single candidate is on the ballot, voter abstention is seen as the only real form of dissent in elections. Although still winning a high percentage of votes, the win was 14 percent smaller than 1984 when Bendjedid garnered 95 percent of the vote with voter turnout at about 95 percent. In 1979, he took 94 percent. While reflecting a decline in popularity, the election still gives Bendjedid a clear mandate to continue with the economic reforms introduced after a week of rioting in early October that claimed 176 lives. Rioters filled the streets to protest high unemployment, inflation and a chronic housing shortage. In an effort to restore calm, Bendjedid promised a more liberal political system and less central control of both the economy and society. In his third term, Bendjedid faces the task of reducing the power of a military and civilian bureaucracy that has built a comfortable position in the 25 years since independence from France. He also has promised to loosen the grip of the National Liberation Front, the only legal political party, on all aspects of Algerian life. One problem is how to permit more autonomy and democratic freedom without allowing opposition parties. The severe economic problems remain, many traceable to several years of low oil prices on world markets. Unemployment and annual inflation have surpassed 20 percent and the foreign debt is $23 billion.