Where does online hold the greatest influence over auto shoppers? A Cars.com VP explains a key factor of messaging and discusses a more measurable approach.

Fewer than 20 percent of automotive ad impressions are generating 80 percent of the impact on decisions about which vehicle to buy. Within this 20 percent, the most influential advertising is on automotive websites, and the reason is timed relevance. These seem like bold claims, I'm sure, but I can back them up, and they reveal some important truths about how we target potential automotive customers.

Although the 80/20 principle -- 80 percent of the consequences come from 20 percent of the causes -- is widely accepted in many areas of business, advertisers generally give all forms of advertising frequency equal weight. The reason for this is pretty simple: it is difficult to know which ad impressions were delivered to just the right people at just the right time with just the right message. So while identifying which 20 percent of the customers are responsible for 80 percent of the profit is commonplace, measuring individual ad impressions is a lot tougher.

While some shoppers refuse to give credit to advertising at all for having influenced a decision, in the 2007 New Auto Shopper study by J.D. Power and Associates, 54 percent of all new-vehicle buyers openly declared that the internet affected their make/model decisions. Even more telling, fully 25 percent of all buyers said the internet had a "big impact" on which vehicle they purchased -- this number includes those buyers who do not have internet access and therefore couldn't possibly have been influenced by its ads.

So it seems that even though the internet is a powerful force for driving automotive purchases, the industry is still only dedicating a small percentage of overall ad spending to the digital channel. Some of online's sphere of influence can be attributed to manufacturer and dealer websites. Indeed, it has been well established that even when a shopper starts at a site like Toyota.com, he or she frequently buys something other than a Toyota. Manufacturer sites are essential to manufacturers (just as dealer sites are essential to dealers); yet, there are no conquest opportunities on these sites (some large dealer group sites being the exception). So how are so many new-vehicle buyers being influenced by the internet?

"When" relevance and reach
Millions of shoppers come to independent automotive websites for credible information, comparisons and advice on what to buy. The key point is that they are openly asking to have their thoughts and opinions influenced while visiting these sites. This is the importance of "when" relevance, and is an area where online has the highest potential to influence people – right when they are thinking about the very need your product addresses.

The concept of "when" relevance, or the importance of timing in behavioral influence, is far from new. In his book, "Predictably Irrational," MIT behavioral economist Dan Ariely comes to the conclusion that a key method of keeping ourselves from making the same irrational mistakes repeatedly is to develop systems that interrupt us at precisely the time we are going to make a decision one way with information that will shift us back in the right direction.

The value of "when"
Effective cost-per-thousand (eCPM) is usually defined as the cost per ads delivered (vs. booked or guaranteed). True eCPM measures the value of a media purchase with respect to "who" relevance -- how efficiently we are reaching the right people. For an advertiser to calculate comparable eCPMs, it should also include an additional element in the calculation -- the proportion of the impressions that reach actual car buyers.

Behavioral targeting (BT) can give advertisers more frequency with the right "who" relevance, allowing them to reach people who are probably in the market for a vehicle over the next few weeks or months. While this is a huge leap forward, BT typically has no more "when" relevance than your average TV or radio ad.

Placing ads on automotive sites like Cars.com, AutoTrader.com, kbb.com and Edmunds.com are at least as "who" relevant as BT, but this strategy also provide the much needed "when" relevance as well. Therefore the impressions must be valued differently, and the returns from offering more appropriate creative need to be factored in as well.

Although the internet's ability to affect the decision about which dealer to buy from is only half as great as it is on the decision about which vehicle to buy, dealers are tending to move their advertising dollars toward the internet faster than most manufacturers are. This may be true because dealers are closer to the actual sale and get more direct feedback.

The importance of "when" relevance should affect creative efforts, as well as ad placements. A retention ad (a Ford ad placed where shoppers are looking at Fords or information about a Ford) should reinforce the shopper’s good judgment and brand intentions. The goal is to keep the shopper going in the direction they appear to be at that moment.

A conquest ad (a Ford ad placed where shoppers are looking at Toyotas or information about a Toyota) must give the shopper compelling information about why they should add your vehicle to their consideration set. The ad should link to additional information that will bring them closer to purchasing your product. The goal here is to get the shopper to shift away from the shopping path they appear to be on at that moment and move onto information more favorable to you.

The cute or funny message that is necessary to get shoppers' attention when they are watching, reading or listening to news, sports or entertainment is probably not the optimal content for shoppers when they are actively seeking information in order to determine which vehicle to buy. Should you really put a lot of effort into an ad that is going to make up a small number of your impressions?

Don't make me talk about the 80/20 rule again.

Dennis Galbraith is VP of dealer products and operations at Cars.com.