of 48% for the year ended December 31, 2013, and was relatively flat as compared to the year ended December 31, 2012.

Prior to July 2011, in the U.S., our streaming and DVDs-by-mail operations were combined and members could receive both streaming content and DVDs under a single “hybrid” plan. In July 2011, we introduced DVD only plans and separated the combined plans, making it necessary for members who wish to receive both streaming services and DVDs-by-mail to have two separate membership plans. As members were able to receive both streaming and DVDs-by-mail under a single hybrid plan prior to the fourth quarter of 2011, it is impracticable to allocate revenues and expenses to the Domestic streaming and Domestic DVD segments prior to the fourth quarter of 2011.

The $200.0 million increase in our domestic revenues in 2012 as compared to 2011 was primarily due to the 15% growth in the domestic average number of unique paying members driven by new streaming memberships. This increase was offset in part by an 8% decline in domestic average monthly revenue per unique paying member, resulting from the decline in DVD memberships.

The $217.9 million increase in domestic cost of revenues in 2012 as compared to 2011 was primarily due to a $397.7 million increase in content licensing expenses. This increase was primarily attributable to continued investments in existing and new streaming content. Content delivery expenses decreased by $162.0 million primarily due to a 41% decrease in the number of DVDs mailed to paying members driven by a decline in the number of DVD memberships. Other costs associated with content processing and customer service center expenses decreased by $13.9 million primarily due to a decrease in hub operation expenses resulting from the declines in DVD shipments, offset partially by increases in customer service center expenses to support our growth in domestic memberships.

Marketing expenses decreased $38.5 million in 2012 as compared to 2011 primarily due to a decrease in marketing program spending in television, radio and direct mail advertising partially offset by increases in online advertising.

The Domestic segment had a contribution margin of 27% for the year ended December 31, 2012, and is relatively flat as compared to December 31, 2011.

International Streaming Segment

The $204.7 million increase in our international revenues in 2012 as compared to 2011 was primarily due to the 260% growth in the international average number of unique paying members driven by a full year of service offering in Latin America as well as our launches in the U.K. and Ireland and Nordic regions. International streaming memberships account for 18% of total streaming memberships at the end of 2012.

International cost of revenues increased by $368.1 million in 2012 as compared to 2011 primarily due to a $347.5 million increase in content licensing costs resulting from the continued investments in streaming content available for viewing in Canada and Latin America and to support our launches in the U.K. and Ireland and Nordic regions.

International marketing expenses increased $122.6 million in 2012 as compared to 2011 primarily due