The article explains why changes in how much people spend can cause ups and downs in the economy. The researchers suggest that when people feel more confident about their future income and investments, they tend to spend more, which boosts the economy. This creates a cycle where economic activity, consumer expectations, and investor returns all feed into each other, making economic fluctuations stronger. This effect is more pronounced for changes in spending than changes in production. The study also shows that government spending can encourage private spending when done early in a downturn.