Despite gains in recent years, most U.S. workers aren't satisfied with their employer's workplace diversity efforts, with nearly half saying they've faced discrimination on the job, a recent survey finds.

Of 2,200 adults polled nationwide by Adecco USA, a Melville, N.Y.-based human resources firm, only a third said they felt corporate America had achieved total workplace diversity. Nearly 80 percent said most employers promoted diversity efforts without enforcing them as effectively, the survey found.

Indeed, as many as 47 percent said they had been discriminated against themselves at work, with 52 percent citing age as the underlying issue. Another 43 percent cited gender, and 32 percent cited race.

Despite these shortcomings, most respondents said workplace diversity efforts had a positive impact on the success of their companies, and more than half said they saw a boost productivity as a result.

"As the idea of a truly diverse workforce continues to evolve, what's become more and more clear to employers is that achieving this is not only about adhering to regulations or being seen as politically correct, but directly ties to their organization's success and their ability to be innovative and profitable," Lois Cooper, head of Diversity & Inclusion at Adecco USA, said in a statement.