Methods of Measuring the Secular Trend

Broadly speaking there are three types of methods for measuring the trend values in a time series. They are: (i) Free hand graphic method, (ii) Average method and (iii) Least square method. The average method, again, consists of three different methods viz: (i) Arbitrary average method, (ii) Semi average method and (iii) Moving average method. Similarly, the method of least square consists of five different types of methods. They are: (i) Straight line method, (ii) parabolic method, (iii) Geometric or logarithmic method, (iv) Exponential method, and (v) Growth curve method. Thus, in all, we have nine different methods of measuring the trend values of a time series. They are:

• Free hand graphic method
• Arbitrary average method
• Semi average method
• Moving average method
• Straight line method of least square
• Parabolic method of least square
• Geometric method of least square
• Exponential method of least square
• Growth curve method of least square