According to preliminary data from 192 member countries, the Universal Postal Union said Saturday that traffic to the United States declined by 81 percent on Aug. 29 compared with the previous Friday, underscoring some of the disruption that accompanied the rule change.

The de minimis exemption expired at 12:01 a.m. that day, meaning that low-value parcels are now subject to a 10 to 50 percent levy that coincides with the tariff rate of the country of origin, or a flat rate of $80 to $200, depending on which option the merchant chooses.