The government's "Cool Biz" campaign to encourage casual office attire this summer is expected to give the economy a 100 billion yen boost, a private think tank said Friday.

The nominal gross domestic product is also estimated to grow by 0.05 percent in the April-June quarter over a year earlier, Dai-ichi Life Research Institute Inc. said.

Per capita spending on clothes is expected to grow by 20,000 yen to 40,000 yen as a result of the campaign, kicked off Wednesday to help reduce global warming, the think tank said.

The institute, affiliated with Dai-ichi Mutual Life Insurance Co., came up with the estimates based on such research as government data and surveys of major department stores.

According to their study, 12.3 percent of local governments and businesses are expected to follow the campaign, which recommends setting office thermostats at 28 to help reduce greenhouse gas emissions.

If all the workers leave their jackets and ties at home between June and September, business in the apparel industry, including retailers and manufacturers, would post an additional 100.8 billion yen in sales, the institute said.

The think tank also estimates that if all businesses and local governments participate in the campaign, related sales will increase 720 billion yen and generate nominal GDP-boosting effects worth 450 billion yen.