MEMURO, Japan — Satomi Sato, a 51-year-old widow, knew she had it tough, raising a teenage daughter on the less than $17,000 a year she earned from two jobs. Still, she was surprised last autumn when the government announced for the first time an official poverty line — and she was below it.

“I don’t want to use the word poverty, but I’m definitely poor,” said Ms. Sato, who works mornings making boxed lunches and afternoons delivering newspapers. “Poverty is still a very unfamiliar word in Japan.”

After years of economic stagnation and widening income disparities, this once proudly egalitarian nation is belatedly waking up to the fact that it has a large and growing number of poor people. The Labor Ministry’s disclosure in October that almost one in six Japanese, or 20 million people, lived in poverty in 2007 stunned the nation and ignited a debate over possible remedies that has raged ever since.

Many Japanese, who cling to the popular myth that their nation is uniformly middle class, were further shocked to see that Japan’s poverty rate, at 15.7 percent, was close to the Organization for Economic Cooperation and Development’s figure of 17.1 percent in the United States, whose glaring social inequalities have long been viewed with scorn and pity here.