Pay Per Click (PPC) advertising is marketed as the best possible way of measuring your return on investment , you cannot question this. Where else can you see exactly where people have come from how much they paid to get there and what they done (bought something , contacted you etc). They key to establishing your ROI is with reporting.
The Google Adwords reporting tool is a huge asset to PPC management and is not bettered by any other PPC advertising programme (in my opinion). However I’ve noticed that when taking data from a scheduled report whether it be daily weekly or monthly that the date that is generated is not always factual.