Nov. 20 (Bloomberg) -- This week's fatal stabbings of former Japanese pension officials and their families threaten to reignite public outrage at missing data on 50 million people, which helped drive two prime ministers from office in a year.

Attacks on Nov. 18 at the homes of two retired officials from the Ministry of Health, Labor and Welfare may be related, Tsuyoshi Yoneda, a director general of the National Police Agency, said in a meeting with investigators televised by NHK television yesterday. Two people died and another was injured.

Prime Minister Taro Aso, who must call an election before September, is bidding to avoid a repeat of last year's ballot, which handed control of the upper house to the opposition Democratic Party of Japan. If it wins the more-powerful lower house, its leader, Ichiro Ozawa, would replace Aso.

``In Japan, where the elderly make up a majority of voters, pensions have always been and continue to be at the forefront of elections,'' said Junichi Takase, a professor of political science at the Nagoya University of Foreign Studies. ``There's always a possibility that Aso will be the third prime minister to be defeated by the pension issue.''

One in five Japanese people is over 65, compared with 12.6 percent of the U.S. population, according to the U.S. Census Bureau. Public support for Aso has fallen 11 percentage points since he took office two months ago to 37 percent, according to an Asahi poll published Nov. 11, as he disclosed contradictory explanations about his 5 trillion yen ($52 billion) economic stimulus plan.

Couple Dies

Former vice minister Takehiko Yamaguchi, 66, and his wife, Michiko, 61, were found dead at their home in Saitama, near Tokyo, with stab wounds to their chests, a local police official said yesterday.

Yasuko Yoshihara, 72, the wife of Kenji Yoshihara, who had held the same government position, was later stabbed at her Tokyo home by a man pretending to be from a parcel delivery service, according to an official at the Tokyo Metropolitan Police Department. The police officials asked not to be identified by name, citing department policy.

Yoshihara received hospital treatment and expressed concern her husband was a target, Kyodo News reported, citing unidentified government sources. Both men had been involved in administering pension plans and the ministry has warned of the possibility of further attacks, Kyodo said.

More Security

Police are strengthening security arrangements for Yoichi Masuzoe, the welfare minister, and other officials, Kyodo said. Aso, 68, canceled his daily walk yesterday so as not to ``burden,'' his security detail, according to a statement from his office.

The killings drew attention to the government's failure to recover records lost after the Social Insurance Agency switched to a new computer system in 1997.

The agency first announced in February 2007 that about 50 million records were incomplete or unidentifiable, in part because officials failed to accurately record names and other vital information. As a result, some premiums paid by individuals weren't credited to their accounts.

Shinzo Abe resigned as Japan's prime minister in September 2007 after the pension scandal led to the upper house election defeat. His successor, Yasuo Fukuda, vowed to make good on Abe's promise to resolve the problem within a year and formed a consumer-protection agency to address health scandals in general.

Failed Promises

In March, Masuzoe said the government had failed to meet Fukuda's promise, matching up only 11.7 million of 50 million pension accounts. As of September, 14 million records still require clarification, according to the agency's Nov. 18 report.

``There's a strong sense of frustration in society against the pension system,'' said Hiroshi Itakura, a professor emeritus of criminal law at Nihon University in Tokyo. The stabbing is ``incredible and unforgivable,'' he said.

To contact the reporters on this story: Sachiko Sakamaki in Tokyo at ssakamaki1@bloomberg.net. Toko Sekiguchi in Tokyo at Tsekiguchi3@bloomberg.net

Last Updated: November 20, 2008 01:29 EST