Singapore Telecom comparision

I found an easy way but not sure accurate or not to compare companies with financial data from Yahoo! Finance.

Yahoo! Finance:
example, CapitaMall Trust, at the bottom of left panel, basic reports are listed, Income Statement, Balance Sheet, Cash Flow. The most useful is all companies are aligned with same format, so it's very easy to compare with same formula, of coz, data integrity maybe a problem.

I just the data to come out ROE, OM & Gearing. The formula I use, not sure whether it's accurate enough or not.
1) ROE = Net income / (Total assets - Total liabilities)
2) OM = Net Income From Continuing Ops / Total revenue
3) Gearing = Total liabilities / Total assets

For Singapore Telecom, data as below (4 years average):
                     ROE / OM / Gearing

Starhub       616% / 14% / 95%

	Dec 31, 2011	Dec 31, 2010	Dec 31, 2009	Dec 31, 2008	AVG
ROE	1436%	487%	254%	288%	616%
OM	14%	12%	15%	15%	14%
Debt/Asset	99%	97%	93%	93%	95%

M1                57% / 17% / 69%    (ROE & OM continue to drop)

	Dec 30, 2011	Dec 30, 2010	Dec 30, 2009	Dec 30, 2008	AVG
ROE	51%	52%	58%	67%	57%
OM	15%	16%	19%	19%	17%
Debt/Asset	67%	68%	69%	72%	69%

Singtel          no data

for the big difference between Starhub & M1, still need further study ...