Middle-income earners aren't acting like they're middle-class.The Good Brigade/Getty ImagesMiddle-income Americans aren't living middle-class lifestyles.Research indicates that middle-income earners spend more like lower-income workers.The share of middle-income Americans is shrinking, with increased polarization between income tiers.The American dream goes something like this: You pull yourself up by your bootstraps, get a solid job with benefits, buy a house, start a family, and coast comfortably toward retirement in the country's robust middle class.While many might think middle-income Americans would be living this dream, they're not.