 During an interview with Yahoo Finance's Jennifer Schomburger on Monday, have you been to the grocery store lately? Schomburger asked Yellen in the interview, I sure have. I go every week. Yellen replied, it's sticker shock, isn't it? Just when you look at shipping costs, those have come down. Global food commodity prices have also come down, but food prices still remain high. Should the U.S. invest in agriculture to boost the food supply in this country? Schomburger asked.