"Buying local" is the kind of thing everyone is in favor of and no one actually does. Well, okay, not "no one," but far fewer than favor it in theory. Like "giving up Facebook," "switching to Linux" and "always using a condom," the number of people who make the claim in order to signal something about themselves is much smaller than the number actually engaging a behavior.
See further Seth Stephens-Davidowitz, Everybody Lies: Big Data, New Data, and What the Internet Can Tell Us About Who We Really Are ( https://www.amazon.com/Everybody-Lies-Internet-About-Really/... ).
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