HomeAway, a marketplace where property owners can list their homes for rent, sought to move beyond last-click attribution and understand the impact of display. Conducting a marketing experiment with Google, it found that its true CPA is less than half the value indicated by last-click attribution.


  • Understand the direct and indirect impact of HomeAway's Google Display Network spend
  • Measure the incremental effects of digital media on HomeAway's bottom line
  • Drive new owner registrations to create valuable inventory for HomeAway.com


  • Developed a media plan to drive owner registrations with ads on the Google Display Network
  • Applied the newly measured CPiAs to develop future budgeting and bidding strategy
  • Tested that media plan with their Google account team using a statistically robust marketing experiment to understand the true (causal) cost per incremental acquisition (CPiA) Monitored and analysed outcomes during and after the test


  • More accurate CPA was revealed using a four-week experiment across 50% of the US market
  • HomeAway found that its true CPA is less than half the value indicated by last-click attribution
  • CPiA was confirmed with a 95% confidence interval
June 2015

HomeAway is a marketplace where homeowners and property managers list their holiday homes for rent by travellers. To increase its supply of rental properties, HomeAway worked with Google to develop a strong display media plan to drive additional homeowner registrations on HomeAway.com.

HomeAway wanted to determine the true incremental contribution of its increased display spend. The company suspected that display ads had a significant impact early in the customer decision process. However, digital media is typically evaluated using a last-click attribution model, which credits 100% of the value of a conversion to the last click, causing mid- and upper-funnel media, such as many types of display,* to be undervalued.

HomeAway worked with Google to conduct a controlled and randomised marketing experiment to move beyond last-click attribution and understand the real impact of display. Using this approach to accurately value all touchpoints, it discovered that display advertising is much more valuable than last-click measurement indicates.


HomeAway and the Google account team began by looking at previous spend and conversion behaviour. Google's unique geo-based approach helped to establish a viable test design, including the test length, test fraction and experiment budget to be used. These parameters ensured a clear evaluation of the marketing opportunity and actionable results from the experiment.

AdWords Last Click reported CPA & True Cost per Incremental Acquisition


The marketing experiment conducted with AdWords, in combination with Google Analytics Premium, establishes a more comprehensive CPA number _ the cost per incremental acquisition (CPiA). This robust number, reported at a 95% confidence interval, informs other attributed CPA numbers such as last-click CPA. HomeAway's test revealed a 51% undervaluation of its display marketing by last-click attribution models. The actual CPA number for HomeAway is lower than indicated through last-click measurement, revealing the true profitability of the display media under test. This discovery enabled HomeAway to properly value its display ads and budget accordingly. The company has absolute confidence in these conclusions because Google's method uses a statistically valid, controlled and randomised experiment to generate results.

Incremental Clicks & AdWords reported paid clicks

The test also revealed that increased display investments resulted in incremental clicks from search. In this case, paid and organic clicks coming from Google.com rose 49%, relative to the control, in test markets with increased display investment. This measurement of incremental clicks shows the extent to which additional media spend can drive paid and organic click traffic. This incremental view is more informative than the reported volume of paid click traffic alone.

Having a robust test backing up the solid performance of Display media beyond last-click opportunities is key for HomeAway to grow its business.

The bottom line: The marketing experiment that HomeAway conducted with its AdWords account team shows the extent to which its digital advertising creates awareness throughout the funnel and contributes to sales beyond the last click.

*To learn more about the role that display and other channels play in the purchase path, see The Customer Journey to Online Purchase aggregate study.

To run a marketing experiment, please reach out to your AdWords account team.