As Japan prepares this week for the biggest initial public offering in the world since Alibaba Group Holding Ltd. in September 2014, the government hopes that the ¥1.5 trillion privatization of the postal service will help revive the country from its 20-year slump.

Prime Minister Shinzo Abe intends for the IPO of Japan Post Holdings Co. and its banking and insurance units Wednesday to unleash the country's enormous pool of household savings and spark investment by individual Japanese, to whom almost 80 percent of the shares are being sold. The privatization of the venerable post office — part of a wave that includes Britain's Royal Mail in 2013, Italy's Poste Italiane last month and China's postal savings bank next year — is also likely to shake up Japan's banking industry and transform the 144-year-old postal service to cope with the digital age.

"The meaning of the Japan Post privatization is linked to the real revival of Japan after lost decades," said Hideki Fujii, an economics professor at Kyoto University who has studied the sale. "Japan is under even more pressure than it was 10 years ago to increase its international competitive edge in every industry."