In an economy, the decisions of households, businesses, or investors rarely rely on the present alone.
They are largely guided by expectations, that is, beliefs about the future evolution of prices, wages, or economic activity. But how are these expectations formed? One of the answers proposed by economists is that of adaptive expectations, a mechanism by which agents construct their forecasts mainly based on past experience.
Learning from the past to forecast the future
Adaptive expectations rest on a simple idea: economic agents gradually adjust their expectations based on the errors they have made in the past. Rather than predicting the future perfectly, they adjust their expectations from the gaps between what they had anticipated and what actually happened.
For example, if inflation turns out higher than expected in a given year, households and businesses will tend to raise their expectations for subsequent periods. Conversely, if inflation is lower than anticipated, their forecasts will be lowered. This gradual learning process reflects a form of bounded rationality, where agents rely on the information available, mainly past, to guide their decisions.
A central role in economic dynamics
Adaptive expectations play an important role in analyzing economic phenomena such as inflation or unemployment. They help explain why certain dynamics can persist over time. If agents expect high inflation because it has been high in the past, they may adjust their behavior accordingly, for example by demanding higher wages or by adjusting their prices, which can sustain inflation itself.
This mechanism highlights a form of inertia in the economy. Adjustments are not instantaneous, as expectations evolve progressively. This can slow the return to equilibrium after an economic shock and complicate the task for public authorities.
A useful approach, but partly outdated
If adaptive expectations have long been a reference in economic theory, they have been progressively complemented, or even challenged, by other approaches, notably that of rational expectations. The latter assume that agents use all available information, including announced economic policies, to form their forecasts.
Nevertheless, adaptive expectations retain analytic relevance, particularly for describing behaviors where information is imperfect or when agents respond with a delay to economic developments. They help explain why certain forecast errors recur and why economic adjustments can be gradual rather than immediate.
