Statistical modelling/Comparison of sources of income

A number of questions provide ranked answers (e.g. Question 8 CS11Quest1, Question 3 CS11Quest2). So far we have produced bar charts to illustrate proportions of different characteristics receiving different rankings, but can we quantitatively combine these results? Rowlands et al. (2003) propose a method for developing an index based on the individual rankings. Their formula is calculated as follows:

Index = sum of [3 if rank 1 + 2 if rank 2 + 1 if rank 3] for a given source of income ÷ sum [3 if rank 1 + 2 if rank 2 + 1 if rank 3] over all sources of income.

Thus, if in a particular homestead the ranking is: crops 1, salary/wages 2 and livestock and products 3, contributions to the index for crops would be 3 for the numerator and (3 + 2 + 1 = 6) for the denominator. For the index for salary/wages the contribution to the numerator would be 2 and the denominator 6 as before, and for livestock 1 and 6, respectively.

This index adds up to 1 when summed over the different sources of income; the higher the value of an individual index for a particular source of income the greater the overall importance of that source of income.

We used Excel to calculate the values of the index for each source of income. Crop and livestock systems provided similar levels of sources of income for the homesteads. Salary/wages also provided important source of income.