Here is a letter I got from Mary Kate Dilworth ….

Dear Dan,
Hello.  My name is Mary Kate Dilworth, and I am a junior at Thomas Jefferson High School for Science and Technology in Alexandria, Virginia. Last summer, I read a copy of Predictably Irrational, and now it sits on my bedside table because I reference it so often in my life.  I find the chapter on social v. market norms particularly applicable to my life (I am in several volunteer organizations that regularly do fundraising projects).

Today, for example, my school’s Russian Honors Society had an Election Day bake sale.  In years past, various goods have had set prices, but this year we chose to make it donation-based.  What a difference it made!  When one woman bought a cupcake, she reached for a one dollar bill and asked about the price.  When I told her there was no set price but donations-only, she put the one back in her wallet and pulled out a ten.  Your suggestion to switch to social instead of market norms was a great one-thank you so much!

Sincerely,
Mary Kate Dilworth

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Dear Mary Kate,

This is great, and I am delighted that you are taking lessons from the book and implementing them.

Next time think about trying both versions and measuring more directly the difference.  It would be interesting to know if the effect is driven by a few people who give much more, by many people who give a bit more, or perhaps by more people becoming interested in the bake sale (or maybe all of these).

And good luck in your next implementation.

Dan