Why do the options bump from 25-50-100 to 220? What byte of microtargeting data is at work there? Did donor patterns indicate that for people donating $100, going up another $20 or $10 might be a psychological barrier, whereas for people at the $200 level a 10% bump-up triggers no hesitation? Does this bring in an extra 3% or 5%? How prevalent is this trick? Is there some accepted wisdom that you can slip one bump-up in the menu but not more?