Demographic reports allow you to see the performance of your ads by age groups and gender on the specific sites in the Display Network that provide this information. As part of a greater effort to simplify AdWords, the DEMOGRAPHIC_PERFORMANCE_REPORT is being deprecated and will no longer be available in the API starting on or around March 21, 2012. You can back up the historical demographic data for your campaigns by downloading these reports before they sunset.
Please be aware that this change doesn’t impact demographic exclusions for your campaigns, which are done via the AgeRange and Gender criteria in the CampaignCriterionService. If you have additional questions about this deprecation, please reach out to us on the AdWords API forum or one of our regular Google+ Hangout office hours.