Shortened working hours caused by power outages caused average monthly wage rates in Japan to shrink in March for the first time in over a year, data released by the Health, Labor and Welfare Ministry said Tuesday.

In a separate report, on the other hand, a Nikkei survey showed a slight increase in the proportion of job offers to seekers, inching up by 0.01 point to 0.63 in March.

The labor ministry said the March average monthly wage rate amounted to 274,886 yen (US$3,390), down by 0.4 percent from the year before.

Scheduled wages, which are based on a basic salary rate, declined by 0.9 percent to 243,425 yen, the labor ministry disclosed further. The reductions were felt most in the restaurant, health care, welfare and education sectors, the report said.

The labor ministry's report noted that before the March 11 earthquake and tsunami, which also damaged the major Fukushima nuclear power plant and triggered power blackouts, its survey showed wage rates on an "improving" pattern.

There could still be areas and sectors that could be impacted in the coming days by the "confusion in the wake of the quake disaster," said an unnamed labor ministry official quoted by the Japan Times.

The labor ministry also noted that March overtime work hours fell from a year ago by 2.0 percent to 10.1 hours, the first cut in 15 months.

In the manufacturing sector, overtime working hours averaged 13.9 hours, lower by 0.8 percent from the year before and by 6.8 percent from the preceding month, the labor ministry said.

Meanwhile, Nikkei Digital Media has reported that its Nikkei Business Index slumped by 6.6 points to 89.8 points in March--its sharpest decline since the survey was first conducted in January 1973.

Reflecting the extent of the downward pressure that the March 11 disaster has exerted on the economy, three of the Nikkei Business Index's four components suffered declines.

Nikkei reported: "Industrial output plunged 15.3 percent, the steepest decline ever recorded, while overtime work dropped 3.6 percent. Commercial sales sank 10.7 percent due to slumping demand for automobiles and home electronics."