The seasonally adjusted unemployment rate from the Labour Force Survey. The threshold follows the Sahm rule loosely: the monthly rate, not a three-month average, half a point above its low of the past twelve months.
Threshold source: worldstat.us construction after the Sahm rule: the monthly rate against its twelve-month low. How thresholds are chosen
Japanese unemployment barely moves across the cycle because firms hoard labour; the series crosses its threshold only in severe downturns.