Translating "Corporate Strategy" methods to the HR world

In reading through "Lean Six Sigma for Service" (Michael L. George), I started thinking about the ways we leverage our HR team's priorities in our LSS deployment. 

George talks about how to benchmark against competitors on ROIC, WACC and EP (Economic Profit, the difference between the ROIC % and WACC %).  These are fairly easy numbers to obtain through annual reports, and can certainly be used as the cornerstone of resource deployment in an organization.
But we live in a slightly different world.  We are, in some respects, one of the largest costs of an organization.  These calculations, while meaningful, don't always help in deploying resources through HR.  I'm curious as to how we benchmark performance with that in mind. 
Do you benchmark against HR teams in your market sector, direct competitors, local companies, similar sized organizations, or some other group?
What are the key metrics you use for that comparison?  HR cost per FTE?  Total HR spend?  Turnover?  Something else?
Finally, how do you leverage that information to drive your deployment, and how often do you re-examine that strategy?