Something surprising happened in Pennsylvania discrimination cases last year. For the first time, age overtook race and sex as the single largest category of job-bias complaints filed with the state; residents filed 1,108 age-discrimination complaints, 26% of all employment cases, compared with 493, or 14%, a year earlier.

Such charges are becoming more and more popular. In fiscal 1985, the federal Equal Employment Opportunity Commission received 16,784 complaints of age bias in the private sector, up from 11,063 three years earlier. The number of people in the protected age group, 40 to 70 years old, is growing even as many companies try to thin management ranks to cut costs or to consolidate following mergers. Employees are more cognizant of their rights and more likely to add age-bias claims to a wrongful-discharge suit.

Unlike earlier civil-rights laws, the federal age-bias act provides jury trials. This makes cases hard to defend, even though many employers win on appeal. "Everyone on the jury has reason to identify with the plaintiff," says Atlanta labor lawyer Charles Edwards.

San Francisco attorney JoAnne Dellaverson warns that "as more and more people reach the protected age group, you'll see more and more litigation." Companies may be forced to change the way they deal with older employees. Instances of discrimination may decrease as more companies recognize the value of experienced employees, who are often more productive than young hotshots. Other companies will protect themselves by tightening procedures and leavening praise with criticism. If not, trouble may lie ahead: one former INC. 500 company settled an EEOC complaint by accepting . . . you guessed it . . . quotas for the middle-aged.