Most consulting firms tout broad transportation sourcing savings in the 5% - 15% range and, with the notable exception of the capacity crunch of a couple of years ago, my experience matches that. Yes, there are a number of factors that impact what you will achieve. Those include:
1. How good have you been? The simple truth is it can be hard to create savings now if they have been captured before.
2. How good will you be? If you have had trouble creating transportation savings in the past you need to, again honestly, figure out what will be different this time.
3. What is your freight profile? Some companies simply have better opportunities than others to drive down costs from sourcing (such as if they have very attractive lanes).
4. What is the state of the market? The current or expected supply-demand scenario will impact how carriers bid.
This question has prompted us to think about this area in more detail. We've offering more detailed thoughts in an upcoming "Transportunities" column on Supply Chain Digest. You will be able to find it here: http://www.scdigest.com/assets/Experts/expertinsights.php
Look for other responses below, or add your perpective or insight!