This method is very simple and easy to understand. It is applicable to linear and non-linear trends. It gives us an idea about the rise and fall of the time series. For every long time series, the graph of the original data enables us to decide on the application of more mathematical models for the measurement of a trend. Monthly data from 5 years has 60 values. A graph of these values may suggest that the trend is linear for the first two years (24 values) and for the next 3 years, it is non-linear. We accordingly apply the linear approach to the first 24 values and the curvilinear technique to the next 36 values.
This method is not mathematical in nature, so different people may draw a different trend. The method does not appeal to the common man because it seems rough and crude.