I found myself asking a basic question when I looked at the Comscore/MediaMetrix traffic figures for the multi-family industry in May: How many people were looking for an apartment online in the month?

The answer was interesting and speaks to the power of diversifying marketing spend in order to reach the largest number of consumers.

In total, Comscore/MediaMetrix reports results for 55 sites serving the rental market, with total traffic of 20.2 million.  The top 10 apartment rental sites had total unique visitors of 15.1 million in May,  75% of the total audience..

Since January, there has been very little change in the total audience of the top 10 sites, although share did shift slightly. The biggest change in share was at Apartment Finder, which had 4% of the visits of the top 10 sites in January and 10% of the visits of the top 10 sitop10 rental site traffic may.jpgtes in May. Even though Apartment Finder gained close to 900,000 unique visitors in the period, the top 10 sites only gained 343,000, speaking to the incremental shifts in share among the leaders.

While total audience is useful in comparing sites to each other, the more relevant metric to use to scale the market is unduplicated audience: the total number of individuals who are searching for an apartment online that month. This is different from the total number of visitors to the leading websites, since consumers may easily visit more than one site.

unduplicated audience.jpgAn analysis of Comscore’s data shows that there were 11.7 million unduplicated apartment shoppers on the top 10 web sites in the month of May.

Notably, 8.5 million of those users, or 73%, went to only one apartment site in the month. The remaining 3.2 million, or 27%, consulted 2 or more sites.

The top 5 sites had 9.1 million unduplicated visits, or 75% of the total unduplicated audience for the top 10 sites. The percent of unduplicated visitors was slightly higher for the top 5 sites, with 77% of the 9.1 million visitors going to only one of the top five apartment listing web sites.

The duplication of visitors between specific sites is fairly low, an analysis of the Comscore figures show. The three sites with the highest duplication are Rent.com and Apartments.com, which share 15% of their users, and Rent.com and MyNewPlace.com, also at 15%. Generally, duplication rates between any other two apartment web sites in the top 10 was below 10%. For instance, Apartment Finder shared 6% of its traffic with Rent.com, 6% with Apartment Guide and 5% with For Rent, according to the Comscore figures.

The numbers suggest that the wide number of options available to consumers online has not contributed to heavy duplication of the audience. This is true also for the distribution of print magazines as well: of the roughly 5 million magazines distributed each month by Apartment Finder, Apartment Guide and For Rent, virtually none are distributed through locations where another apartment magazine is available.

A conclusion? For those marketers who are looking to drive a significant volume of leads, distributing your marketing spend across multiple marketing partners should give you relatively high access to a unique audience, given the low duplication of usage.

This scale of usage is interesting relative to the available stock of apartment housing. According to the National Multi-Family Housing Council, there were more than 12 million apartments in buildings with 10 or more units, and the top 50 property management companies managed close to 6 million apartment units in the first quarter of 2009.

The methodology of theComscore/MediaMetrix reports is laid out here, for those who are interested.

Also, to reinforce the disclosure on my blog, for those of you who are reading this out of context, I am the CEO of Network Communications, Inc., the publisher of Apartment Finder.