The Harvard Coop began distributing yesterday an 8.3 per cent rebate to its members; the rebate was 0.3 per cent higher than last year's.

The rebate has increased steadily since a 1970 low of 2 per cent although this year's jump is the smallest in the eight year period.

General Manager James A. Argeros said yesterday the rebate increase was a result of the continually swelling size of the Coop's membership, which from 74,000 in 1977 to 80,000 this year.

The Coop's policy in recent years of distributing all profits generated by its members means that $1.45 million will be shared among members this year--$100,000 more than in 1977, Argeros said.

"The Coop is reaching a point of maximum returns, which accounts for the leveling off in the increase in rebates," Karlo J. Duvnjak '80, a member of the Coop's board of directors said last night.

"I'm pleased with the size of the rebate, but I'm embarassed that I spent so much," David A. Karns '79 said yesterday after receiving his rebate. The size of the rebates varied "from 91 cents to $200," Heidi J. Licht, a Coop employee, said yesterday.