Under Veblen's theory, conspicuous consumption was theorized to comprise socio-economic behaviours practiced by high wealth or high-income people. More recent economic research indicated that conspicuous consumption is in fact less common among the affluent and more common among lower-income groups, regardless of racial or ethnic background, and also common to the societies of countries with emerging economies: "It signals that the owner came from a poor group and has something to prove." In "The Millionaire Next Door: The Surprising Secrets of America's Wealthy" (1996), Thomas J. Stanley and William D. Danko reported that Americans with a net worth of more than one million dollars are likely to avoid conspicuous consumption, and that millionaires tend to practice frugality—for example, preferring to buy used cars with cash rather than new cars with credit, in order to avoid material depreciation and paying interest for a loan to buy a new car.