U.S. Postal Service To Start Slowing Down Mail Delivery Friday

The US Postal Service is implementing new service standards, which include reduced post office hours and longer delivery times for certain mail types. While cross-country mail will take longer, 60% of first-class mail within the same region will still arrive in two days.

What percentage of first class mail is expected to still take two days to arrive?

Under what condition will mail sent within the same region still take two days to arrive?