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 b