The agency, which aims at boosting the rate to 80 percent, will soon publicize the figure for the fiscal year ended last March, which logged a third straight yearly fall, the sources said.

The rate indicates the percentage of months the premium payment was actually made to the total number of months the payment should have been made in a fiscal year, excluding people who were waived from payment.

The agency believes behind the fall is the recession, which left many people jobless, a situation that automatically switched the pension plan for such workers to the National Pension plan from the employees' pension plan, but they could not make the premium payment because of financial difficulties, the sources said.

The monthly premium is set at 14,660 yen for the current fiscal year that began in April.

After the current public pension scheme was introduced in 1986, the National Pension premium payment rate hit 85.7 percent -- the highest record so far -- in fiscal 1991 and fiscal 1992.

But the rate tumbled to 62.8 percent in fiscal 2002, when the job of collecting premiums was transferred to the agency from municipal governments.

After a brief recovery, it has followed a downward path again in recent years amid the scandals, including one that revealed the sloppy way payment records had been kept at the agency.