BMW may be duking it out with Mercedes-Benz for the luxury crown, but the automaker should be keeping a close watch on Audi, which is gaining serious shopper interest across the nation. According to a recent analysis conducted by AutoTrader.com, shopper interest is higher for Audi than BMW in 30 states, mostly in the northern half of the country. However, leads in several key states give BMW big geographic strongholds from which to defend against the encroaching automaker.

"While Audi trails BMW in sales, we are seeing definite encroachment in shopper interest, which is a clear indication that Audi is capturing the attention of more and more BMW shoppers," said Rick Wainschel, vice president of automotive insights at AutoTrader.com. "In the past, Audi has taken on Mercedes very directly, but they have been more aggressive recently about going after the positioning platforms that BMW has traditionally been known for. Our data indicates that this strategy is working."

Though Audi still trails the national race, AutoTrader.com's regional analysis shows that the inroads they are making are fairly universal and have effectively cut into BMW's national dominance. The analysis of shopper interest shows that on the national level, BMW's lead over Audi shrunk by 47 percent year-over-year.

A segment-level analysis revealed several key areas where Audi is gaining ground:

• Midsize Car Segment
  In the midsize car segment, Audi is posing a significant threat to BMW, with three of its four segment entries (A6, A7 and S6) growing.  Analysts zeroed in on the A6, as it is the most heavily cross-shopped with the BMW 5 Series on AutoTrader.com. Year-over-year, the 5 Series share of segment interest is down 13 percent, while the share for the A6 is up 36 percent. As such, the 5 Series' advantage in the segment dropped 46 percent against the A6, going from approximately eight points a year ago to four points in April 2013.

• Full-Size Car Segment
  For full-size cars, Audi also posted notable gains with the A8 and the S8. BMW's 7 Series share is down 23 percent year-over-year, cutting BMW's lead advantage over Audi in this segment by 85 percent. AutoTrader.com analysts noted that the S8 has helped Audi gain significant momentum in this segment.  

• Midsize SUV Segment
  Audi is also posing a challenge to BMW in the midsize SUV segment. The BMW X5 and X6 have all lost ground year-over-year. While the loss is not as dramatic as the sedans (the X5 is down seven percent and the X6 is down 21 percent), BMW previously led this segment in shopper interest until January 2013, but it has now dropped to the No. 3 rank. The X5 share advantage over the Audi Q7 has declined 33 percent year-over-year, going from 4.2 share points to 2.8.

"While BMW has a strong lead in several key states such as California, Texas, Florida and New York, Audi seems committed to working very aggressively to keep the tides turning in their favor," Wainschel continued. "To defend its national prominence, BMW will need to focus on strengthening its base in those key states while defending more strategically in areas where Audi has successfully captured more shopper interest." 

Methodology
This analysis is based on shopper interactions occurring on the AutoTrader.com site among new vehicle prospects (shoppers interacting with the latest three model-years of vehicles, currently 2012–2014). Interactions are counted when shoppers take a conscious action related to a vehicle on the site such as clicking through to a vehicle detail page or performing a "build & price." The Audi/BMW analysis was conducted using site behavior from April 2013 and, for comparison, April 2012.