I imagine many dog owners are familiar with the anxiety resulting from a sudden realization that their dog is going to drop a #2 at any moment, and you've forgotten your dog poop bags at home. Everything stops while you madly search from some little bit of poly-something-or-other on the street with which to clean up after the dog. In that moment, a poop bag is precious, and I'll spend the remainder of my walk looking for something else that can serve that purpose in case my dog has a second round in the chamber.
A new condo complex near me has recently solved this problem for the whole neighborhood by simply putting out garbage cans with poop bag dispensers on every corner. Cynics might think this would end poorly: cheapskate dog walkers would pilfer the bags so the dispensers would always be empty, kids would haul them down the block and leave them blowing in the wind. But the parade of horribles doesn't present itself. People take a bag when they need one, pick up their dog poop, and put it in the trash. Nobody hordes the poop bags because there are plenty. Simply providing seemingly-unlimited bags for free turns an economy of scarcity into an economy of abundance at very low cost, and makes the world a better place for everyone in the process.
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What other goods do we think of as scarce that could actually cheaply and realistically be made abundant, making the world a better place in the process?