The article looks at how different income levels affect how much people spend. They used data from UK families between 1974-1993 and found that not just the average income, but also how spread out incomes are, affects spending. They used different methods to estimate these effects and found that the relationship between income and spending changes over time. This means that when we make models to predict how much people will spend, we need to consider not just how much money they have, but also how evenly that money is distributed.