Search marketing software company Engine Ready released an interesting study on how toll-free numbers are treated.

Engine Ready used its call tracking software to create a test to determine if the use of various toll-free prefixes produced different conversion rates, measuring the impact of those different prefixes on call-in conversions and online conversions.

The sample included 18,100 visits to one lead generation site. All visits were from paid search ads in Google and resulted in 2,614 combined call-in and online conversions. The visits were split evenly among 4 distinct landing pages, each page displaying a different toll free number. Other than the different phone numbers, the landing pages were identical. All visits were recorded during the 1st quarter of 2009.

Two interesting results from the study include:

- The highest conversion rate corresponded to the 800 prefix (the oldest of the 800s) and the lowest conversion rate corresponded to the 866 prefix (the newest of the 800s). Thus, the age of the prefix appears to directly impact the call-in conversion rate.

- The toll-free prefix that accompanied the page yielding the highest online conversion rate was "888", followed closely by "866". The impact on online conversions was less than conclusive.

Some good insights can be drawn from the study; namely, that these 800 prefixes do matter. As a result, it's important to perform testing to see if there are opportunities to increase conversion rates. A write up of the 800 prefix and SEM study is available at EngineReady.com.