Jim,
This is such a tough question to really answer, but I would love to see what type of answers you get. There are a few different things that can alter a Dealerships closing %. What might be a better thing to look at is the closing % of OEM, Third Party (Preferably broken out by source), Phone Calls, etc...
For example your own website should have one of the highest close % from the internet lead sources you are getting (not talking about sales phone calls). If you are receiving more Third Party leads compared to what someone is going to tell you the "Industry Average" is than I would assume your close % would be a little lower. This is really due to the fact that Third Party leads tend to close at a lower percentage.
Other factors that can really alter your closing % is what type of vehicle you are selling. I would say a good place to start with closing % is to reach out to your OEM representative and see what your zone or regions close % is on those leads and how you compare. Your Third Party lead providers might be able to give you your competitors close % if you ask them nicely haha. The reason I'm telling you this is because where your dealership is located, and how many competitive dealers are close to you is another factor.
If you have live in an populous area with 2 competitive dealers close by you should close at a higher rate compared to someone that operates in an equally populous area with 4-5 competitive dealers close by to them. I apologize for not answering your question directly, but I see a lot of people ask this question and I would hate for people to make a change in process based off a number that could be completely unobtainable or to low for your Dealership. At the end of the day there are so many different factors that can determine this number, and while one thing might not misconstrue the close % drastically all of the little factors do add up.
I hope what I just quickly wrote was able to at least help steer you in the right direction of where to start looking.
