三大限制：
1)Income taxes：nominal cash outflow ---not real cash flows(should convert using the inflation index)
2)Net working capital:nominal cash outflow ---not real cash flows(should convert using the inflation index)
3)Capital expenditures:difficult to forecast
五大比率：
1)NOPLAT/invested capital -------overstated in nominal terms
2)Net PPE to revenue ------------understated in nominal terms
3)the ratio of NWC to revenue---correctly forecast
4)capital turnover ---------------overstated in nominal terms
5)operating margins-------------overstated in nominal terms
