Revenue Recognition Operating revenues primarily consist of wireless service revenues, revenues generated from device and accessory sales, revenues from wholesale operators and third-party affiliates, as well as long distance voice, data and Internet revenues. Service revenues consist of fixed monthly recurring charges, variable usage charges and miscellaneous fees such as activation fees, directory assistance, roaming, equipment protection, late payment and early termination charges, and certain regulatory related fees, net of service credits. We generally recognize service revenues as services are rendered, assuming all other revenue recognition criteria are met. We recognize equipment revenue and corresponding costs of devices when title and risk of loss passes to the indirect dealer or end-use subscriber. Incentives to retain and acquire subscribers, such as new devices at discounted prices, are recorded as a reduction to equipment revenue upon activation of the device with a service contract. We recognize revenue for access charges and other services charged at fixed amounts ratably over the service period, net of credits and adjustments for service discounts, billing disputes and fraud or unauthorized usage. We recognize excess wireless voice usage and long distance revenue at contractual rates per minute as minutes are used. Additionally, we recognize excess wireless data usage based on kilobytes and one-time use charges, such as for the use of premium services, when rendered. As a result of the cutoff times of our multiple billing cycles each month, we are required to estimate the amount of subscriber revenues earned but not billed from the end of each billing cycle to the end of each reporting period. These estimates are based primarily on rate plans in effect and our historical usage and billing patterns. Regulatory fees and costs are recorded gross. The largest component of the regulatory fees is universal service fund, which represented about 2% of net operating revenues in 2013 , 2012 and 2011 . The