The value of merchandise stolen from retailers in the greater Washington area rose 6 percent in the past year to a record $432 million, the Metropolitan Washington Board of Trade reported yesterday.

Although the rate of increase in the 12 months ended July 31 was the largest since 1975, the theft data are not adjusted for inflation. Thus, with consumer prices here generally running more than 10 percent above those of a year ago, the actual theft rate is unclear.

Retail executives said yesterday they have experience an increase in shoplifting, and area police officials said they have noticed substantial increases in the number of persons arrested for retail theft.

"People are finding themselves strapped, and being strapped, they're turning to theft," Hecht Co. Senior Vice President Edgar Mangiafico told reporters as the Board of Trade launched its 10th annual antishoplifting campaign.

Generally, retail experts say that at least half of all store thefts are inside jobs involving company employes. These robberies account for a large portion of the dollar volume lost.

But shoplifting by customers is a growing headache for retailers nationwide, even if the average price of each item stolen is lower than that for employe theft.

Local retail businesses' antitheft campaign has been credited with reducing shoplifting, particularly during the volatile holiday sales season from late September through Christmas. According to Mangiafico, area retailers paid $6.5 million in the past year for security and employed some 2,000 persons in antitheft work.

According to Board of Trade information compiled from more than 1,000 store locations in the region, there is no "typical" shoplifter.