a4u Blog

The length of a cookie on an affiliate program can sometimes be wrongfully overlooked in favour of the commission rate when affiliates are weighing up whether or not to promote a particular retailer. In order to try and ascertain whether or not cookie length is an important dynamic we carried out some basic analysis of some of our sales for a programme that has performed reasonably well for us on Affiliate Window.

(I would like to thank Louisa here at existem for conducting a lot of this research)

This particular merchant is in the retail sector and offers a reasonably high cookie length of 60 days (on the upper tier) and so this gave us the opportunity to measure the gap between when an online shopper first visits the site through the affiliate link and when they make the purchase.

You can see the results of this analysis below:

As you can see, the majority of transactions took place during the first 24 hours of the cookie being dropped. According to research by ScanAlert in July 2007 this does not fit with the overall picture and that the average time that it takes for a customer to make a purchase from when they first visited the retailer is 34 hours and 19 minutes. This new research interestingly shows shoppers taking up to 80% longer to make a purchase than similar research conducted in 2005. However, by looking at the graph above we can see that a significant number of purchases occurred in the over 30 days window – 99 transactions to be exact. Although this only represents 7% of the total sales that were made this still means that 7% of sales were lost as a result of the length of the cookie, if you base it on the cookie length of the majority of programs – 30 days.

Likewise you need to consider that the buying cycle for some sectors can be higher and take up to 12 weeks, for example Finance, Travel or Entertainment.

We also looked at the cookie lengths of 404 Affiliate Window retail programmes. As you can see on the graph below, as is probably to be expected the majority of programmes have a 30 day cookie. It would be interesting to find out what the default option Affiliate Window offer their merchants in terms of cookie length – if it is 30 days then this would explain the results of the graph below.

What must also be considered is how much thought actually goes into the setting of cookie length from the merchant perspective? From the affiliate’s point of view the fact that programmes such as Buyagift and Ultimate Flowers are offering 9999 day cookies on is great, as long as their cookie is not overwritten* or deleted then they will potentially earn commission from every sale that that particular individual makes.

*A cookie in this scenario is most likely to be over-written by another affiliate involved in an open or closed brand bidding group. As let’s face it the user unless they have bookmarked the original affiliate’s site are highly likely to type the site name back into Google to reach the merchant site.

Other avenues are naturally that the user is a member of a cashback site and I would guess that over 1 Million UK online shoppers are. Or that the cookie is overwritten by fresh activity from a content or price comparison affiliate.

Oneposter.com is the only merchant in our survey that offers a one day cookie. Offering a cookie length as low as this is bound to cause issues with affiliates – even if they don’t necessarily pay a huge amount of attention to the length of cookie on the affiliate programmes that they promote. Respect here goes to Affiliate Future who do not allow merchants to decrease their cookie period to anything less than 30 days.

Ultimately the importance of the cookie length that a merchant assigns when setting up a programme shouldn’t be underestimated, yes there are issues associated with having very long cookie lengths but there are very obvious reasons why having a cookie length of under 30 days will affect the success of an affiliate program in the eyes of the affiliate and in some channels such as generic paid search it could mean the ROI falls to a level that makes it unworkable.

Naturally cookie length makes up just one component in the overall decision to promote a merchant but its length can make a significant impact to the conversion, ROI and ulimatley the success of an affiliate programme.

Finally what would also be interesting next time is to uncover is the percentage of cookies that are over-written by brand activity so we can examine the affect this has on other affiliates.