Different counts for transactions between Magento 1.9 and Google Universal Analytics

[mpankow]

We use Magento 1.9 (Community Edition) with the integratetd Google API and have activated Google Universal Analytics.

Unfortunately my transaction counts are always about 15-20% higher in Magento as in Google Analytics.

Questions: 

- has anyone any idea how to solve this or why it is so?
- how are transactions tracked in Magento?

- how are transactions tracked in Google?

- what system triggers what? Magento ==> Google oder Google ==> Magento

We've also a Webtrekk implemenation for control. Google and Webtrekk have the same results.

Thank you

[chiefair]

Google Analytics is a Client Side operation and therefore suspect.

If I as a user decide to run adblock software and specifically shut down Google Analytics traffic, that data will not be collected when I access your website. Same goes for slow server response from Google or slow user ISP connections, data will be dropped. GA is a best guess, your web server knows explicitly what traffic it serviced.