Commission Rates. The average commission dollars per-member-per-month that we receive for new health insurance plan members varies based upon a number of factors, including the ratio of policies that we sold for which we receive per member-per-month commissions compared to percentage-of-premium commissions, the premiums on the policies we sold, the mix of our members by health insurance carrier and the commission rates we receive from each carrier. Additionally, commission rates may vary by carrier, by geography and by the type of plan purchased by a member.
An accounting policy is considered to be critical if the nature of the estimates or assumptions is material due to the levels of subjectivity and judgment necessary to account for highly uncertain matters or the susceptibility of such matters to change, and the effect of the estimates and assumptions on financial condition or operating performance. The accounting policies we believe to reflect our more significant estimates, judgments and assumptions and are most critical to understanding and evaluating our reported financial results are as follows:
2014 compared to 2013-Technology and content expenses increased $7.8 million, or 24%, in the year ended December 31, 2014 compared to the year ended December 31, 2013, due primarily to an increase of $6.9 million in compensation, benefits, stock-based compensation, and other personnel costs, as a result of an increase in technology and content personnel. The remainder of the increase was due to increased spending to support website operations and increases in data center infrastructure maintenance costs and depreciation expense.
We expect a slight decrease in the amortization of intangible assets in 2016 compared to 2015.
The following table presents a summary of our future minimum payments under non-cancellable operating lease agreements and contractual service and licensing obligations as of December 31, 2015 (in thousands):
For individual and family, Medicare Supplement, small business and ancillary plans, our compensation generally represents a flat amount per member per month or a percentage of the premium amount collected by the carrier during the period that a member maintains coverage under a plan (commissions) and, to a much lesser extent, override commissions that health insurance carriers pay us for achieving certain objectives. Premium-based commissions are reported to us after the premiums are collected by the carrier, generally on a monthly basis. We generally continue to receive the commission payment from the relevant insurance carrier until the health insurance plan is cancelled or we otherwise do not remain the agent on the policy. We recognize commission revenue for individual and family, Medicare Supplement, small business and ancillary plans as the commissions are reported to us by the carrier, net of an estimate for future forfeiture amounts due to policy cancellations. We determine that there is persuasive evidence of an arrangement when we have a commission agreement with a health insurance carrier, a carrier reports to us that it has approved an application submitted through our ecommerce platform and the applicant starts making payments on the plan. Our services are complete when a carrier has approved an application. The seller’s price is fixed or determinable and collectability is reasonably assured when commission amounts have been reported to us by a carrier.
Accounts Receivable-We do not require collateral or other security for our accounts receivable. As of December 31, 2014, three customers represented 30%, 17%, and 14%, respectively, for a combined total of 61% of our $8.2 million outstanding accounts receivable balance. As of December 31, 2015, three customers represented 24%, 18%, and 15% respectively, for a combined total of 57% of our $9.6 million outstanding accounts receivable balance. No other customers represented 10% or more of our total accounts receivable at December 31, 2014 and December 31, 2015. We believe the potential for collection issues with any of our customers was minimal as of December 31, 2015. Accordingly, our estimate for uncollectible amounts at December 31, 2015 was not material.
On March 31, 2014, we purchased an Internet domain name, www.Medicare.com, for $4.8 million. Cash consideration paid in connection with the purchase of the domain name totaled $4.5 million. The consideration paid also included $0.3 million of outstanding receivables from the owner of the domain name that were settled upon completion of the purchase. The related intangible asset was assigned an indefinite useful life. The carrying amounts, accumulated amortization, net carrying value and weighted average remaining life of our definite-lived amortizable intangible assets, as well as our indefinite-lived intangible trademarks, are presented in the tables below for (dollars in thousands, weighted-average useful life is as of December 31, 2015):
In 2013 and 2014, we issued restricted stock units with both service and performance-based vesting criteria to our executive officers. The performance-based contingency period for our restricted stock units with both service and performance-based vesting criteria granted in the fiscal year 2013 was the fiscal years ending December 31, 2013 and 2014, and the measurement of achievement was based on our revenue results for the fiscal years ending December 31, 2013 and 2014. The performance-based contingency period for our restricted stock units with both service and performance-based vesting criteria granted in the fiscal year 2014 were for the fiscal years ending December 31, 2014 and 2015, and the measurement of achievement was based on our revenue results for the fiscal years ending December 31, 2014 and 2015. One-fourth of the shares earned and eligible to vest based on 2013 revenue for performance-based restricted stock units granted in 2013 became vested in 2014. The remaining shares granted in 2013 that are earned and eligible to vest based on 2013 revenue are scheduled to vest in equal annual installments between 2015 and 2017. In 2013, the total number of restricted stock units reported in the table below includes 324,375 units of performance shares of which only 113,742 units were earned and the remaining 210,633 units were cancelled in 2014 because the performance criteria was not fully met. In 2014, the total number of restricted stock units reported in the table below includes 228,750 units of performance shares of which none were earned with the remaining 228,750 units being cancelled in 2015 because the performance criteria was not met. $1.1 million of stock compensation expense recorded in 2013 related to performance-based restricted stock units was reversed in 2014 as a result of related financial metrics not being achieved for the year ended December 31, 2014. Expense recorded for performance-based restricted stock units is recognized on an accelerated basis over the required service periods based on the number of shares earned, or expected attainment for shares to be earned based on performance-based contingency periods that have not been completed.
The following table summarizes stock-based compensation expense recorded during the years ended December 31, 2013, 2014 and 2015 (in thousands):
Included in the balance of income tax liabilities, accrued interest, and accrued penalties at December 31, 2015 is $3.2 million related to tax positions for which it is reasonably possible that the statute of limitations will expire in various jurisdictions within the next twelve months.