Omnicom Group shareholders gained a total return of 26% during the year. But that was short of the market average. On the bright side, that's still a gain, and it's actually better than the average return of 8% over half a decade It is possible that returns will improve along with the business fundamentals. I find it very interesting to look at share price over the long term as a proxy for business performance. But to truly gain insight, we need to consider other information, too. Take risks, for example - Omnicom Group has 1 warning sign we think you should be aware of.