Brand Group Adjusted OIBDA improved significantly versus the prior year period, primarily due to the growth in display and search revenue discussed above as well as a reduction in marketing and general and administrative expenses, including Patch. Lower year-over-year Brand Group operating expenses were partially offset by growth in TAC associated with AOL’s search marketing-related efforts.
Membership Group revenue declines reflect a 7% decline in subscription revenue driven by 13% fewer domestic AOL-brand access subscribers year-over-year. Membership Group revenue declines were partially offset by a 22% year-over-year reduction in churn rate to 1.4% and by 9% year-over-year growth in domestic average access subscription monthly revenue per AOL-brand access subscriber (ARPU). Reduced churn and ARPU growth continues to reflect the benefits of our retention program and the impact of a price rationalization program.
Membership Group Adjusted OIBDA declines primarily reflect the decline in subscription revenue discussed above, partially offset by a decline in costs associated with the decline in subscribers and the disposition of a claim regarding a legal matter in Q3 2013.
AOL Networks revenue increased 19% year-over-year, driven by 32% growth in Third Party Network, including $17.6 million from Adap.tv following its acquisition on September 5, 2013. Excluding Adap.tv, Third Party Network revenue grew 17% year-over-year, driven by growth in the sale of premium formats, primarily video, across our programmatic platform. AOL Network’s year-over-year revenue comparison was negatively impacted by the absence of revenue from the divestiture of StudioNow in Q1 2013 and by a decline in revenue from the sale of Brand Group and Membership Group inventory through AOL Networks. StudioNow contributed $2.3 million in revenue to AOL Networks in Q3 2012.
AOL Networks Adjusted OIBDA decreased year-over-year due to higher research and product development costs primarily related to continued investment in premium formats as well as Ad Learn Open Platform (our demand-side platform) and AdTech MARKETPLACE (our supply-side platform). AOL Networks Adjusted OIBDA declines were partially offset by the increase in AOL Networks revenues discussed above and by more than 500 basis point reduction in Third Party Network TAC as a percentage of Third Party Network revenue.