inventory levels, and sales mix; costs from expanding fulfillment capacity; and payment processing and related transaction costs. 

We seek to expand our fulfillment capacity to accommodate greater selection and in-stock inventory levels and to meet anticipated shipment volumes from sales of our own products as well as sales by third parties for which we provide the fulfillment services. We evaluate our facility requirements as necessary. 

Marketing 

We direct customers to our websites primarily through a number of targeted online marketing channels, such as our Associates program, sponsored search, portal advertising, email marketing campaigns, and other initiatives. Our marketing expenses are largely variable, based on growth in sales and changes in rates. To the extent there is increased or decreased competition for these traffic sources, or to the extent our mix of these channels shifts, we would expect to see a corresponding change in our marketing expense. 

The increase in marketing costs in absolute dollars in 2014 , 2013 , and 2012 , compared to the comparable prior year periods, is primarily due to increased spending on online marketing channels, such as our sponsored search programs, payroll and related expenses, and television advertising. 

While costs associated with Amazon Prime memberships and other shipping offers are not included in marketing expense, we view these offers as effective worldwide marketing tools, and intend to continue offering them indefinitely. 

Technology and Content 

We seek to efficiently invest in several areas of technology and content such as technology infrastructure, including AWS, expansion of new and existing product categories and offerings, and initiatives to expand our ecosystem of digital products and services, as well as in technology infrastructure so we may continue to enhance the customer experience and improve our process efficiency through rapid technology developments while operating at an ever increasing scale. We expect spending in technology and content to increase over time as we continue to add employees and technology infrastructure. Digital media content where we record revenue gross, including Prime Instant Video, is included in cost of sales. 

Technology costs consist principally of research and development activities including payroll and related expenses for employees involved in application, production, maintenance, operation, and platform development for new and existing products and services, as well as AWS and other technology infrastructure expenses. 

Content costs consist principally of payroll and related expenses for employees involved in category expansion, editorial content, buying, and merchandising selection. 

The increase in technology and content costs in absolute dollars in 2014 , 2013 , and 2012 , compared to the comparable prior year periods, is primarily due to increased spending on technology infrastructure, including AWS, and increases in payroll and related expenses, including those associated with our initiatives to expand our ecosystem of digital products and services. We expect these trends to continue over time as we invest in these areas by