The Rational Expectations Theory is a foundational part of modern macroeconomics. It is based on the assumption that people make decisions based on rational processes and current information. Rational expectations theory suggests that economic agents have access to all available information when making economic decisions. This implies that economic agents will be able to anticipate the consequences of their decisions in the future.

At its core, this idea assumes that individuals possess rational expectations and based on past events, can reasonably estimate future possibilities. It is assumed that individuals act upon the best available information considering their expected utility. This is different from traditional economic approaches, as they believed that expectations were based on past experiences.

Rational expectations theory helps economists better understand how economic agents respond to economic changes. Individuals will anticipate the consequences of their economic behavior in making economic decisions, which helps to explain why economic policies have an effect. For example, higher inflation rates would bring about greater caution from households and businesses, as they try to minimize their losses from inflation. Similarly, lower interest rates would cause households and businesses to become more optimistic in the future development of the economy.

In addition to its ability to explain how economic agents are likely to react to policy changes, the rational expectations theory can be used to predict the changes in economic variables. This would allow economists to accurately forecast the effects of new policies on a macroeconomic level.

Overall, the Rational Expectations Theory is an important concept in modern macroeconomics. It provides a way to understand how individuals make decisions based on current information and anticipated outcomes. It also gives economists the ability to predict the changes in economic variables when new policies are implemented. This helps policymakers to understand the effects of their decisions and to properly manage the economy.