The findings are the latest example of how the notion of a single price is breaking down in the digital age, a trend economists say could be pushing up some prices.
On a Thursday in early September, more than 40 strangers logged in to Instacart, the grocery-shopping app, to buy eggs and test a hypothesis.
Connected by videoconference, they simultaneously selected the same store — a Safeway in Washington, D.C. — ... [1558 chars]