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Forecasting

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Forecasting is the formal process of making predictions based on past and present data. While people often use the word "prediction" as a general term, forecasting usually involves specific statistical methods. These methods can use time series, cross-sectional, or longitudinal data to estimate future events. Once a forecast is made, it can be compared to actual outcomes. This comparison creates a variance analysis, which shows the difference between the guess and the reality.

Forecasting is vital because it helps people and organizations prepare for what might happen next.

There are two primary categories of forecasting: qualitative and quantitative. Qualitative forecasting is subjective and relies on human judgment or expert opinion. This method is useful when historical data is not available, such as during long-range decision-making. Examples include the Delphi method, market research, or historical life-cycle analogies. In contrast, quantitative forecasting uses numerical data to model the future. These models assume that patterns found in past data will continue. This approach is typically used for short-term or intermediate-range decisions.

Within quantitative methods, several specific models exist to handle different types of data. The average approach predicts that all future values will equal the mean of past data. A more basic version is the naïve approach, which is highly cost-effective. In a naïve forecast, the prediction for the next period is simply equal to the last observed value. The seasonal naïve approach is a variation used when data has high seasonality. For example, it would set all future April values to equal the previous April's value.

Another method is the drift method, which allows forecasts to increase or decrease based on the average historical change.

Forecasting is used across many different fields, from finance to environmental science. In business, companies use customer demand planning to manage supply chains. Accurate forecasts help retailers reduce excess inventory and increase profit margins. In finance, experts forecast foreign exchange movements using two distinct styles. Chartists study only the price action of a market through charts. Fundamentalists look for the underlying reasons behind market movements. Financial institutions often combine both types of research into a single projection.

Other specialized applications include climate and energy management. Egain forecasting is used for buildings to reduce energy needs and greenhouse gas emissions. Hydrology uses specific terms where "forecast" refers to values at certain future times, while "prediction" refers to general estimates like flood frequency. Scientists also use forecasting for earthquake prediction, weather, and meteorology. Even political and conflict situations are studied using early warning signals.

It is important to distinguish forecasting from budgeting and planning. A budget is a specific, fixed-term financial plan used for resource allocation and control. A forecast, however, provides an estimate of performance that allows for flexibility. Similarly, forecasting predicts what the future *will* look like, while planning predicts what the future *should* look like. Because the future is uncertain, good practice requires indicating the degree of uncertainty in any forecast.

Some people view forecasting as a skill that can be improved through practice. In his work, Philip E. Tetlock discusses how people can become better "calibrated." Calibration means that if a person gives a 10% chance to an event, it actually happens 10% of the time. Some also use forecasting in the form of betting on sports or politics. In a system called futarchy, forecasts of government actions are used to decide which actions to take. In its strongest form, the action with the best forecasted result is automatically chosen.

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