evidence: The biggest drag on its finances is a unique rule that requires the USPS to prepay for workers’ retirement benefits for decades into the future. In 2006, Congress passed a law to require the the agency to pre-fund 75 years worth of retiree health care benefits in the span of about 10 years. [...] The rule took effect in 2007, just before the start of the Great Recession, when the Postal Service was still reporting profits. But the economic downturn hit hard and made the payments unaffordable. It’s true that no other unit of government or private company that provides retiree health care coverage has to make such pre-funding payments. And in recent years, the USPS has not made the required payment, citing a lack of available cash.