Aug. 19 (Bloomberg) –Copper may rise on speculation that supply of the metal will remain constrained, a survey showed.

Nine of 18 analysts, investors and traders surveyed by Bloomberg, or 50 percent, said prices will gain next week. Four predicted a drop and five forecast little change. Copper for three-month delivery was down 1 percent for this week at $8,775 a metric ton by 5:45 p.m. yesterday on the London Metal Exchange.

World copper demand is set to exceed output by 377,000 tons this year, according to the International Copper Study Group. Santiago-based Codelco, the world's largest producer, may miss its output target for this year after union action and weather- related problems, Chairman Gerardo Jofre said last week in an interview.

"Copper's supply/demand fundamentals remain bullish," William O'Neill, a partner at Logic Advisors in Upper Saddle River, New Jersey, said by e-mail Aug. 17. Logic "retains forecast for higher prices into year end," he said.

The red bars on the attached chart are derived by subtracting bearish forecasts from bullish estimates, with readings below zero signaling the majority of respondents expect a decline. The green line shows the copper price. The survey data shown are as of Aug. 12.

The weekly copper survey has forecast prices accurately in 72 of the past 150 weeks, or 48 percent of the time.

This week's survey results: Bullish: 9 Bearish: 4 Hold: 5