Have you ever baked a cake from scratch? If you have, you know that in order for the cake to rise and be edible you have to follow the recipe to a T. Baking is a science that demands a precise combination of ingredients working together to make an end product you'd be proud to serve to your guests.

The same is true with analyzing your online marketing campaigns, and email campaigns in particular. If you only analyze your email program using opens, clicks and conversions, you may be leaving key ingredients out of your analysis -- key ingredients that play into the stacking effect of your online media.

The stacking effect is the combined effect of layering multiple channels to influence consumer behavior (either online or offline). It is the phenomenon that can really put some oomph behind your email program. This is because it is likely that your email program also influences sales that are attributed to your banner programs and search programs. In truth, your search, display media and email programs are all helping each other out. Understanding this relationship can help you better optimize not only your email program but also your display and search programs and your marketing budget as a whole. And most important, it can help you justify and garner support for the growth of your email program in the longer term.

In our multiple stacking effect studies over the years, most have shown that there is indeed a stacking effect, or a synergy, when consumers see multiple media across channels. Here are two examples:

For a large company, a recent study looked at multiple touchpoints leading to a conversion. When looking at click data alone, we saw that when users clicked on only one channel they had a conversion rate of 4.7%. When they clicked on two channels, their conversion rate almost doubled, to 8.5% -- and when they clicked on three channels, their conversion rate almost tripled, to 11.5%. (Channels included search, display, email, affiliates, portals, and two additional industry-specific channels.)

For a large multichannel retailer the study looked at users who only saw display media versus those who saw display media plus email. Stacking both email and display media brought significant lift compared to not stacking the channels.

Understanding the stacking effect or synergies among your different marketing channels is very complicated. Here are some things that you must keep in mind when beginning to tackle this complex analysis:

1. Resist the temptation to know everything at once. Start simple and answer one question at a time.
2. Start out by testing a few variables in a simple test-and-control methodology. Isolate your variables and make sure that the only difference between your test and control cells is the single variable you're testing. An example would be:

· Banner Only

· Email Only

· Banner Plus Email

3. Define your evaluation metrics up front, but be open to looking broadly to really understand the impact. It's important to agree on what metric is important for your organization, but it's also important to look at secondary metrics that might show significant lift even when primary metrics don't.
4. Understand that this is just a snapshot in time. Many things may affect your response, including the maturity of your brand, your competition, your offers/creative and list. Therefore it's important to retest occasionally.

So what is the recipe for success? The answer is: it depends. It depends on your business, your goals for individual programs and the goals of your organization as a whole. What I can say is that identifying what is valuable to your business and looking beyond just opens, clicks and conversions is the first step. Add in a little strategy, a dash of analytics and you're on your way. Happy baking.