The labor ministry has revised downward the January average monthly wage at domestic firms, including overtime pay, to 275,934 yen, a fall of 0.2 percent from a year earlier.
In a preliminary report released earlier this month, the Health, Labor and Welfare Ministry said the average wage rose 0.2 percent in January to 277,003 yen, marking a first rise in 25 months.
The ministry attributed Friday's downward revision in part to a rise in the number of part-time employees.
The latest drop is smaller than the 0.6 percent fall in December, however, reflecting a continued increase in overtime pay, it said.