title: Google Analytics Enhanced Ecommerce - How to track cart quantity update?
body: <p>Google doesn't say a word on how to deal with the user changing the quantity of a line in their cart using the Enhanced Ecommerce plugin. </p>
  
  <p>When a user adds something to his cart, returns to the same cart in a later session and adds more of the same product it might occur that he gets a lower unit price (for example when price breaks are used by the e-commerce site).</p>
  
  <p>So, for example, he first adds 1 unit for $3, comes back and raises the number to 10 and thereby only has to pay $2 for each unit.</p>
  
  <p>Now the price previously sent to GA needs to be invalidated in some way.</p>
  
  <p>There are multiple solutions for this, but each of them have some serious drawbacks:</p>
  
  <p>1) Calculate the difference and add / remove that.</p>
  
  <p>2) Remove the line and then add with current quantity.</p>
  
  <p>Method 1 has the advantage of passing the (most) correct user interaction. Since add/remove doesn't seem to have a nonInteraction parameter, using method 2 would mean wrong numbers of adds/removes.</p>
  
  <p>Method 2 has the advantage of being able to change the price if a price change has happened after the product has been added the first time. For example: after adding more units the customer now has a lower unit price. Using method 1 would mean that either the amounts in GA are incorrect, or you would have to calculate price differences and fictionally give the latest added units a lower price.</p>
  
  <p>Which of the two methods is preferable?</p>