If you use AdWords API reports to retrieve performance statistics for AdWords Express campaigns, please read on as these changes will affect you.
What's changing?
In preparation for upcoming improvements, an ongoing migration process is modifying campaigns managed by AdWords Express.
Currently, when you enable an AdWords Express promotion, it creates up to two AdWords campaigns:
  - 
    A Search Network campaign with:
    
      - AdvertisingChannelType = SEARCH(appears asSearch)
- AdvertisingChannelSubType = SEARCH_EXPRESS(appears asSearch Express)
 
- 
    A Display Network campaign with:
    
      - AdvertisingChannelType = DISPLAY(appears asDisplay)
- AdvertisingChannelSubType = DISPLAY_EXPRESS(appears asDisplay Express)
 
As part of the migration, the two campaigns above will be paused and replaced by a 
single AdWords campaign with:
  - AdvertisingChannelType = EXPRESS(appears asExpress)
- AdvertisingChannelSubType = UNKNOWN(appears as an empty string)
After the campaigns for a promotion are migrated, performance statistics for the AdWords Express promotion will be available in reports as follows:
  - Performance statistics for dates prior to the migration will be attributed to the original campaigns with SEARCH / SEARCH_EXPRESSandDISPLAY / DISPLAY_EXPRESS.
- Performance statistics for dates after the migration will be attributed to the new campaign with EXPRESS / UNKNOWN. The new campaign will only appear in the CAMPAIGN_PERFORMANCE_REPORT.
For example, assume an AdWords Express promotion manages the following two AdWords campaigns today:
  | Campaign ID | Campaign Status | Advertising Channel Type | Advertising Channel Sub Type | 
  | 1000 | ENABLED | SEARCH | SEARCH_EXPRESS | 
  | 2000 | ENABLED | DISPLAY | DISPLAY_EXPRESS | 
After the migration, the account will contain the following campaigns for the AdWords Express promotion:
  | Campaign ID | Campaign Status | Advertising Channel Type | Advertising Channel Sub Type | Performance statistics | 
  | 1000 | PAUSED | SEARCH | SEARCH_EXPRESS | Before the migration | 
  | 2000 | PAUSED | DISPLAY | DISPLAY_EXPRESS | Before the migration | 
  | 3000 | ENABLED | EXPRESS | UNKNOWN | After the migration | 
What should you do?
Ensure that your application properly handles all three combinations of 
AdvertisingChannelType and 
AdvertisingChannelSubType. For example:
  - If your application inspects AdvertisingChannelTypeorAdvertisingChannelSubTypeto handle AdWords Express campaigns, please adjust the logic to handle the new combination ofEXPRESS / UNKNOWN.
- If you use predicates on AdvertisingChannelTypeorAdvertisingChannelSubTypeto include or exclude AdWords Express campaigns, make sure that your predicate takes the new combination into account.
Reminder: The AdWords API only supports retrieving AdWords Express entities. You cannot modify AdWords Express entities in your account using the AdWords API.
If you have any questions about this change, please contact us via the 
forum. 
 - Josh Radcliff, AdWords API Team
 - Josh Radcliff, AdWords API Team