The tax and social security systems have long been seen as favoring full-time homemakers over working women because they are based on single-income households.
But dual-income households have been the norm since 1997, leading many experts to call the systems outdated.
According to a Health, Labor and Welfare Ministry report, there were 6.15 million dual-income households in 1980 versus 11.14 million single-income households. By last year, however, there were 10.12 million dual-income households and 7.97 million households with full-time housewives.