The economy is hot, but the people are bothered. Americans think the country is in dreadful economic shape despite strong wage growth, low unemployment, and steadily declining inflation. We know this from survey after survey. What we don’t really know is how people formed those judgments. To find out, The Atlantic commissioned a new poll. When the results came in, one finding jumped off the screen: Americans are really, really unhappy about grocery prices. Working with Leger, a North American polling firm, we asked 1,005 Americans how they felt about the economy. As with other recent polls, this one painted a gloomy picture. Only 20 percent of people said that the economy has gotten better over the past year, compared with the 44 percent who said it has gotten worse. (There was a big partisan split, but even among self-identified Democrats, only 33 percent said the economy has improved.) Then we asked them to choose, from a long list, what factors they consider when deciding how the national economy is doing. The runaway winner was …