ROIC Tax Element

For the tax element, some people take an assumption / effective industry rate, others use actual tax expense. Where do you chaps stand?

Personally, if you take the actual tax expense paid, it makes comparisons between companies hard, but you are also giving the company the benefit of its intelligent (stupid) tax planning.

Obviously better to pick one and stick with it but I'm siding on picking a flat rate across an industry as i want to see how effectively management have used their capital compared to others.