Yesterday, a Planet Money segment explained something I’ve wondered about for years. A guest on the show, who wanted to start a mug company, found that shipping a mug within the US costs more than both buying and shipping a mug from China. I’ve noticed this phenomenon on everything from Amazon tchotchkes to Whole Foods mangos: Items that travel farther than a grey whale migration (5000 miles one way) are competitively priced with items that don’t.

Why? The answer is the Universal Postal Union.

UPU is a UN agency that coordinates international postal policies, limiting excess charges for international shipping. For years, that worked out for the US, with the USPS realizing revenue of over $200 million annually when most mail flowed Out. And when money is clumping on your shore, you tend not to complain about having to shovel it in.

Since the rise of e-commerce, most US mail is flowing In. Today, the USPS has an annual deficit of $80 million on international mail. The UPU modified the rules in 2016 in response to e-commerce, but it is still much, much cheaper to send a package from Beidaihe to Santa Cruz than the reverse.

To Send is better than to Receive under this economic structure because, as a moment’s reflection will reveal, the costs of mail delivery are much higher on the receiving end, where a human in a truck or on foot personally visits each destination. At the post office, bags of sorted mail leave together for the first part of their trips via truck, plane, or boat, reducing the per-piece cost.

The actual cost for a mug to travel across the world, in terms of energy expenditure alone, is clearly most than the cost for it to travel from North Beach to Noe Valley, though the pricing may be lower. This economic distortion is not just anti-climate, it’s anti-small business. I love that handmade hummingbird feeder made by a craftsman in Minnesota, but I can get a similar item made overseas for less money, quicker delivery, and Free Shipping.

I’m making this choice because I’m unemployed. If we all keep making similar choices, we all will be.