An increasing number of bankers working at foreign firms in Japan are unhappy with their bonuses, and falling expectations for raises are giving them more cause to gripe, according to a Morgan McKinley survey.

Forty percent of respondents were dissatisfied with their bonuses, up from 28 percent in 2016's survey. About 51 percent received indication from their employers that their base salary will rise this year, a 5 percentage point drop.

"It is clear that bankers took home a smaller bonus this year, a downward trend that continues," Lionel Kaidatzis, managing director of Morgan McKinley Japan, said in an interview. "The disappointment seems to stem from the fact that despite a number of financial service institutions bouncing back quite strongly in 2016, their bonuses have either been flat or down."

Despite the gripes over pay, the bankers were optimistic on Japan's economic outlook. About 84 percent of the respondents were neutral, positive or very positive on the world's No. 3 economy over the next 12 months, compared with 63 percent last year.

Morgan McKinley based its survey on the responses of 257 employees at about 40 mainly foreign financial firms, which it didn't identify. The poll was conducted through interviews, emails and phone calls with M&A bankers, salespeople, traders, research analysts, fund managers and operations staff from Feb. 15 to March 7.