The M score was created by Professor Messod Beneish. In many ways it is similar to the Altman Z score, but optimized to detect earnings manipulation rather than bankruptcy.
Beneish used all the companies in the Compustat database between 1982-1992.
The M score is based on a combination of the following eight different indices:
DSRI = Days’ Sales in Receivables Index
* Measured as the ratio of days’ sales in receivables in year t to year t-1. A large increase in DSR could be indicative of revenue inflation.
GMI = Gross Margin Index
* Measured as the ratio of gross margin in year t-1 to gross margin in year t.
* Gross margin has deteriorated when this index is above 1. A firm with poorer prospects is more likely to manipulate earnings.
AQI = Asset Quality Index
* Asset quality is measured as the ratio of non-current assets other than plant, property and equipment to total assets.
* AQI is the ratio of asset quality in year t to year t-1.
SGI = Sales Growth Index
* Ratio of sales in year t to sales in year t-1.
* Sales growth is not itself a measure of manipulation. However, growth companies are likely to find themselves under pressure to manipulate in order to keep up appearances.
DEPI = Depreciation Index
* Measured as the ratio of the rate of depreciation in year t-1 to the corresponding rate in year t.
* DEPI greater than 1 indicates that assets are being depreciated at a slower rate. This suggests that the firm might be revising useful asset life assumptions upwards, or adopting a new method that is income friendly.
SGAI = Sales, General and Administrative expenses Index
* The ratio of SGA expenses in year t relative to year t -1.
LVGI = Leverage Index
* The ratio of total debt to total assets in year t relative to yeat t-1.
* An LVGI >1 indicates an increase in leverage
TATA – Total Accruals to Total Assets
* Total accruals calculated as the change in working capital accounts other than cash less depreciation.
The eight variables are then weighted together according to the following:
M = -4.84 + 0.92*DSRI + 0.528*GMI + 0.404*AQI + 0.892*SGI + 0.115*DEPI – 0.172*SGAI + 4.679*TATA – 0.327*LVGI
A score greater than -2.22 indicates a strong likelihood of a firm being a manipulator. In his out of sample tests, Beneish found that he could correctly identify 76% of manipulators, whilst only incorrectly identifying 17.5% of non-manipulators.
The five variable version excludes SGAI, DEPI and LEVI which were not significant in the original Beneish model.
M = -6.065 + 0.823*DSRI + 0.906*GMI + 0.593*AQI + 0.717*SGI + 0.107*DEPI
In 2008, Beneish goes into more detail in another paper that he published titled “Identifying Overvalued Equity” which seeks to use the M score to select stocks.
Beneish examines portfolio deciles based around his M score over the period 1993-2003 with annual rebalancing done four months after the financial year end.
The results produce 14% for the 8 variable model and 14.8% for the 5 variable M score version where the top M score stocks were held long while the lowest M score stocks were shorted.