Japan's divorce rate is still quite low - around two divorces for every 1,000 people.
Shame is one reason. A failed marriage is frowned upon here, particularly among the older generation.
But money is another important factor. Wives often have real concerns that they will not be able to support themselves if they leave the marital home.
The change in the law will help. It will make it easier for women to force their husbands to share their pensions.
One survey suggested that in as many as 42,000 couples, wives have been waiting for the rules to change.
Last autumn, the social insurance agency began offering a confidential service which helped couples calculate how much of the husband's pension should be given to the wife.
Some 90% of the applications have been from women. And there is another factor at work. Japan's baby boom generation is starting to retire this year.
That adds up to around five million mostly male workers, who have spent their lives working long hours, and often drinking long after work, several nights a week.
These absentee spouses will now have much more time to spend at home - all day, every day - perhaps for the first time in the couple's married life. Many here believe that will prove too much for their wives to cope with.