There is a fundamental difference in the way that Google Analytics and AdWords report traffic mediums and which mediums lead to conversions; one of reasons why the numbers will always vary. To understand which medium will be counted when, you need to know that Google Analytics uses Last Click attribution and Google AdWords uses First Click attribution.
But what does this mean in real terms? Well, when a user comes to your site several times before converting, as is common, they may use different media to get there.
Google Analytics Conversion Attribution
The following table shows which medium will be attributed the conversion in Google Analytics when the visitor comes in through each combination of mediums – assuming three visits and a conversion on the third.
Although it’s not quite that simple, so I’ve highlighted the occasion on which the last click attribution is overwritten and instead the penultimate medium is reported as the converting medium. This is because Direct visits do not overwrite the utmz cookie that passes on this data, so if Direct is the final medium used before a conversion the conversion will actually be attributed to the previous medium.
AdWords Conversion Attribution
Within the AdWords interface conversions are reported on based on an ad being the first point of contact – this means that if a user comes to the site through an ad and then comes back organically or through other mediums, AdWords will attribute this conversion to AdWords.
If a user clicks one ad and comes back to the site via a different ad to convert then the attribution is given to the final ad, the medium is still AdWords. In order to see the details of conversions like this you can use AdWords Conversion Funnels. To find this information, go to Reporting and Tools > Conversions and on the left hand side click Search Funnels. This takes you through to an area with a number of extra ways to analyse your conversions. Assisted clicks is the area relevant in this situation as this can show all the clicks that led to a conversion.
In this section I like to look at Top Paths, here you can go in to your campaign and then break down the assists by ad group, keyword or a wide range of other Dimensions:
Finally, if a user comes to your site via an organic search before they click an ad, AdWords will not pick up the information about previous visits and will attribute everything it sees to your clicks on ads.
Obviously this makes life difficult when you’re trying to put the whole picture together, which is why Google Analytics now has a funky new area called Multi Channel Funnels. This can tell you which mediums assisted conversions and give you more insight in to sources of conversions and user behaviour. To see this area you need conversion tracking in Analytics and you need to be using the new interface.