According to a data from Dataium, the conversion rate of the average unique visitors to shoppers was 59% during the month of December 2012. This information is based on statistics for national automotive Internet behavior for December 2012. 
Below are a few key statistics from Dataium’s data for December 2012
Average Unique Visitors to per Websites: 4,199
Avg Unique Visitors to Shoppers (conversion): 59%
Page views per shopper: 10
VINs viewed per active visitor: .12
Average shoppers to lead:
LTAV (lead to active visitor): 3.86%
LTV (lead to visitor): 2.26%
Search Percentages:
New: 46%
Used: 54%
Click here for more information from Dataium.