Forecasting
Moving averages provide a good description of the trend in a time series. However a common goal in time series analysis is to forecast values of the time series in the future. For example, accurate forecasting of the demand for a product allows production capacity to be adjusted in time to meet changes to the demand.
Moving averages cannot smooth the end values of the series and do not provide a method to extend the trend into the future. The best that can be done is to extend the trend 'by eye' — hardly an objective forecasting method!
Least squares
If the trend in a time series is linear, a least squares line can be fitted to model it.
World rice production
Recoding years
There can be problems if the year is used as an explanatory variable for annual data. Using a recoded year as explanatory variable can avoid these problems.
World rice production