The Table Below Shows the Data on the Four Leading

Essay

The table below shows the data on the four leading indicators for the four-month period. Construct a diffusion index.
$$\begin{array} { | l | l | l | l | l | } \hline & { \text { Leading Indicators } } \\\hline \text { Month } & \text { A } & \text { B } & \text { C } & \text { D } \\\hline 1 & 40 & 150 & 10 & 75 \\\hline 2 & 45 & 140 & 9 & 60 \\\hline 3 & 40 & 150 & 10 & 55 \\\hline 4 & 20 & 160 & 11 & 50 \\\hline\end{array}$$