28 our network is comprised of in-building riser facilities , metropolitan optical fiber networks , metropolitan traffic aggregation points and inter-city transport facilities . our network is physically connected entirely through our facilities to 2,251 buildings in which we provide our on-net services , including 1,541 multi-tenant office buildings . we also provide on-net services in carrier-neutral data centers , cogent controlled data centers and single-tenant office buildings . we operate 51 cogent controlled data centers totaling 565,000 square feet . because of our integrated network architecture , we are not dependent on local telephone companies or cable companies to serve our on-net customers . we emphasize the sale of our on-net services because we believe we have a competitive advantage in providing these services and these services generate gross profit margins that are greater than the gross profit margins of our off-net services . we believe our key growth opportunity is provided by our high-capacity network , which provides us with the ability to add a significant number of customers to our network with minimal direct incremental costs . our focus is to add customers to our network in a way that maximizes its use and at the same time provides us with a profitable customer mix . we are responding to this opportunity by increasing our sales and marketing efforts including increasing our number of sales representatives and expanding our network to locations that we believe can be economically integrated and represent significant concentrations of internet traffic . one of our keys to developing a profitable business will be to carefully match the cost of extending our network to reach new customers with the revenue expected to be generated by those customers . in addition , we may add customers to our network through strategic acquisitions . we believe some of the most important trends in our industry are the continued long-term growth in internet traffic and a decline in internet access prices on a per megabit basis . the effective price per megabit for our corporate customers is declining as the bandwidth utilization and connection size of our corporate customer connections increases . as internet traffic continues to grow and prices per unit of traffic continue to decline , we believe we can continue to load our network and gain market share from less efficient network operators . however , continued erosion in internet access prices will likely have a negative impact on the rate at which we can increase our revenues and our profitability . our revenue may also be negatively affected if we are unable to grow our internet traffic or if the rate of growth of internet traffic does not offset an expected decline in our per unit pricing . we do not know if internet traffic will increase or decrease , or the rate at which it will increase or decrease . changes in internet traffic will be a function of the number of internet users , the amount of time users spend on the internet , the applications for which the internet is used , the bandwidth intensity of these applications and the pricing of internet services , and other factors . the growth in internet traffic has a more significant impact on our net-centric customers who represent the vast majority of the traffic on our network and who tend to consume the majority of their allocated bandwidth on their connections . net-centric customers tend to purchase their service on a price per megabit basis . our corporate customers tend to utilize a small portion of their allocated bandwidth on their connections and tend to purchase their service on a per connection basis . we are a facilities-based provider of internet access and communications services . facilities-based providers require significant physical assets , or network facilities , to provide their services . typically when a facilities-based network services provider begins providing its services in a new jurisdiction losses are incurred for several years until economies of scale have been achieved . our foreign operations are in europe , canada , mexico and asia . europe accounts for roughly 80 % of our foreign operations . our european operations have incurred losses and will continue to do so until our european customer base and revenues have grown enough to achieve sufficient economies of scale . due to our strategic acquisitions of network assets and equipment , we believe we are well positioned to grow our revenue base . we continue to purchase and deploy network equipment to parts of our network to maximize the utilization of our assets and to expand and increase the capacity of our 29 network . our future capital expenditures will be based primarily on the expansion of our network and the addition of on-net buildings . we plan to continue to expand our network and to increase the number of on-net buildings we serve including multi-tenant office buildings and carrier neutral data centers . many factors can affect our ability to add buildings to our network . these factors include the willingness of building owners to grant us access rights , the availability of optical fiber networks to serve those buildings , the cost to connect buildings to our network and equipment availability . results of operations year ended december 31 , 2015 compared to the year ended december 31 , 2014 our management reviews and analyzes several key financial measures in order to manage our business and assess the quality of and variability of our service revenue , operating results and cash flows . the following summary tables present a comparison of our results of operations with respect to certain key financial measures . the comparisons illustrated in the tables are discussed in greater detail below . replace_table_token_5_th nmnot meaningful ( 1 ) includes non-cash equity-based compensation expense of $ 584 and $ 488 for 2015 and 2014 , respectively . story_separator_special_tag our increase in interest expense is attributed to interest expense related to the issuance of our $ 200.0 million of senior unsecured notes outstanding since april 9 , 2014 and interest expense related to the issuance of our $ 65.0 million of senior secured notes outstanding since august 19 , 2013 , partly offset by the decline of interest expense from our convertible notes that we repaid in june 2014. income tax ( expense ) benefit . our income tax benefit was $ 49.7 million for 2013 and our income tax expense was $ 3.7 million for 2014. the net income tax expense for 2014 includes united states federal income taxes of $ 2.5 million and state income taxes of $ 1.1 million . the net income tax benefit for 2013 includes income tax benefits of approximately $ 50.2 million resulting primarily from the reduction of the valuation allowance on net deferred tax assets related to our operations in the united states , and $ 0.5 million of income tax expense related to our european and canadian operations . at each balance sheet date , we assess the likelihood that we will be able to realize our deferred tax assets . we consider all available positive and negative evidence in assessing the 35 need for a valuation allowance . as of december 31 , 2013 , we recorded an income tax benefit of $ 50.2 million ( including $ 49.3 million related to our us federal deferred tax assets ) since we determined that we no longer required a valuation allowance against our us deferred tax assets . we continue to maintain a valuation allowance against our european and other foreign deferred tax assets and our deferred tax assets limited under section 382 of the internal revenue code in the united states . section 382 limits the utilization of net operating losses when ownership changes , as defined by that section , occur . we have performed an analysis of our section 382 ownership changes and we have determined that the utilization of certain of our net operating loss carryforwards in the united states is limited . our net operating losses related to our foreign operations are generally not subject to similar limitations . of the $ 390.6 million of net operating losses available at december 31 , 2014 in the united states approximately $ 286 million are unavailable for use and approximately $ 81 million are limited for use under section 382. our net operating loss carryforwards outside of the united states totaling approximately $ 789 million are not subject to limitations similar to section 382. buildings on-net . as of december 31 , 2014 and 2013 we had a total of 2,125 and 1,990 on-net buildings connected to our network , respectively . liquidity and capital resources in assessing our liquidity , management reviews and analyzes our current cash balances , short-term investments , accounts receivable , accounts payable , accrued liabilities , capital expenditure and operating expense commitments , and required capital lease , interest and debt payments and other obligations . the following table sets forth our consolidated cash flows . replace_table_token_9_th net cash provided by operating activities . our primary source of operating cash is receipts from our customers who are billed on a monthly basis for our services . our primary uses of operating cash are payments made to our vendors , employees and interest payments made to our capital lease vendors and our note holders . our changes in cash provided by operating activities are primarily due to changes in our operating profit and changes in our interest payments . cash provided by operating activities for 2015 , 2014 and 2013 includes interest payments on our note obligations of $ 29.3 million , $ 26.3 million and $ 15.6 million , respectively . story_separator_special_tag the funds from the escrow account ( such date of release , the `` escrow release date `` ) and to group after the escrow release date . as a condition to releasing the funds from escrow we redeemed our remaining outstanding convertible notes on june 20 , 2014 ( the `` redemption transaction `` ) . after consummation of the redemption transaction , cogent finance merged with group , with group continuing as the surviving corporation ( the `` finance merger `` ) . at the time of consummation of the finance merger , group assumed the obligations of cogent finance under the 2021 notes and the indenture governing the 2021 notes ( the `` indenture `` ) and group and each of group 's domestic subsidiaries became party to the indenture pursuant to a supplemental indenture to the indenture and the obligations under the indenture became obligations solely of group and each of group 's domestic subsidiaries . holdings also provided a guarantee of the 2021 notes but holdings is not subject to any of the covenants under the indenture . after the conditions to the release of the escrow proceeds were satisfied , on june 25 , 2014 ( the `` escrow release date `` ) the proceeds from the 2021 notes were released . the net proceeds from the offering were $ 195.8 million after deducting discounts and commissions and offering expenses . the net proceeds from the offering are intended to be used for general corporate purposes . the 2021 notes were issued pursuant to , and are governed by the indenture between cogent finance and the trustee . the 2021 notes bear interest at a rate of 5.625 % per year and will mature on april 15 , 2021. interest began to accrue on the 2021 notes on april 9 , 2014 and will be paid semi-annually on april 15 and october 15 , commencing on october 15 , 2014. following the escrow release date , the 2021 notes became group 's senior unsecured obligations and are guaranteed on a senior unsecured basis by the company . the 2021 notes are effectively subordinated

net cash used in investing activities . our primary use of investing cash is for purchases of property and equipment . these amounts were $ 35.6 million , $ 60.0 million and $ 49.0 million for 2015 , 2014 and 2013 , respectively . the annual changes in purchases of property and equipment are primarily due to the timing and scope of our network expansion activities including geographic expansion and adding buildings to our network . in 2015 we obtained $ 21.9 million of network equipment and software in a non-cash exchange for a note payable under an installment payment agreement . net cash ( used in ) provided by financing activities . our primary uses of cash for financing activities are for dividend payments , stock purchases and principal payments under our capital lease obligations . in 2015 we redeemed our $ 240.0 million senior secured notes for a payment of 36 $ 251.3 million and in 2014 we repaid our senior convertible notes for $ 92.0 million . amounts paid under our stock buyback program were $ 39.4 million for 2015 and $ 58.6 million for 2014. there were no stock purchases in 2013. we began paying a quarterly dividend on our common stock in the third quarter of 2012. during 2015 , 2014 and 2013 we paid $ 66.3 million , $ 54.2 million and $ 35.4 million , respectively , for our dividend payments . our dividend payments have primarily increased from quarterly increases in our regular quarterly dividend per share amount . principal payments under our capital lease obligations were $ 20.2 million , $ 18.2 million and $ 11.2 million for 2015 , 2014 and 2013 , respectively , and are impacted by the timing and extent of our network expansion activities . our financing activities also include proceeds from and repayments of our debt offerings . in 2015 we received net proceeds of $ 248.6 million from the issuance of our $ 250.0 million senior secured notes . in 2014 we received net proceeds of $ 195.8 million from the issuance of our $ 200.0 million senior unsecured notes .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```net cash used in investing activities . our primary use of investing cash is for purchases of property and equipment . these amounts were $ 35.6 million , $ 60.0 million and $ 49.0 million for 2015 , 2014 and 2013 , respectively . the annual changes in purchases of property and equipment are primarily due to the timing and scope of our network expansion activities including geographic expansion and adding buildings to our network . in 2015 we obtained $ 21.9 million of network equipment and software in a non-cash exchange for a note payable under an installment payment agreement . net cash ( used in ) provided by financing activities . our primary uses of cash for financing activities are for dividend payments , stock purchases and principal payments under our capital lease obligations . in 2015 we redeemed our $ 240.0 million senior secured notes for a payment of 36 $ 251.3 million and in 2014 we repaid our senior convertible notes for $ 92.0 million . amounts paid under our stock buyback program were $ 39.4 million for 2015 and $ 58.6 million for 2014. there were no stock purchases in 2013. we began paying a quarterly dividend on our common stock in the third quarter of 2012. during 2015 , 2014 and 2013 we paid $ 66.3 million , $ 54.2 million and $ 35.4 million , respectively , for our dividend payments . our dividend payments have primarily increased from quarterly increases in our regular quarterly dividend per share amount . principal payments under our capital lease obligations were $ 20.2 million , $ 18.2 million and $ 11.2 million for 2015 , 2014 and 2013 , respectively , and are impacted by the timing and extent of our network expansion activities . our financing activities also include proceeds from and repayments of our debt offerings . in 2015 we received net proceeds of $ 248.6 million from the issuance of our $ 250.0 million senior secured notes . in 2014 we received net proceeds of $ 195.8 million from the issuance of our $ 200.0 million senior unsecured notes .
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 Suspicious Activity Report : 28 our network is comprised of in-building riser facilities , metropolitan optical fiber networks , metropolitan traffic aggregation points and inter-city transport facilities . our network is physically connected entirely through our facilities to 2,251 buildings in which we provide our on-net services , including 1,541 multi-tenant office buildings . we also provide on-net services in carrier-neutral data centers , cogent controlled data centers and single-tenant office buildings . we operate 51 cogent controlled data centers totaling 565,000 square feet . because of our integrated network architecture , we are not dependent on local telephone companies or cable companies to serve our on-net customers . we emphasize the sale of our on-net services because we believe we have a competitive advantage in providing these services and these services generate gross profit margins that are greater than the gross profit margins of our off-net services . we believe our key growth opportunity is provided by our high-capacity network , which provides us with the ability to add a significant number of customers to our network with minimal direct incremental costs . our focus is to add customers to our network in a way that maximizes its use and at the same time provides us with a profitable customer mix . we are responding to this opportunity by increasing our sales and marketing efforts including increasing our number of sales representatives and expanding our network to locations that we believe can be economically integrated and represent significant concentrations of internet traffic . one of our keys to developing a profitable business will be to carefully match the cost of extending our network to reach new customers with the revenue expected to be generated by those customers . in addition , we may add customers to our network through strategic acquisitions . we believe some of the most important trends in our industry are the continued long-term growth in internet traffic and a decline in internet access prices on a per megabit basis . the effective price per megabit for our corporate customers is declining as the bandwidth utilization and connection size of our corporate customer connections increases . as internet traffic continues to grow and prices per unit of traffic continue to decline , we believe we can continue to load our network and gain market share from less efficient network operators . however , continued erosion in internet access prices will likely have a negative impact on the rate at which we can increase our revenues and our profitability . our revenue may also be negatively affected if we are unable to grow our internet traffic or if the rate of growth of internet traffic does not offset an expected decline in our per unit pricing . we do not know if internet traffic will increase or decrease , or the rate at which it will increase or decrease . changes in internet traffic will be a function of the number of internet users , the amount of time users spend on the internet , the applications for which the internet is used , the bandwidth intensity of these applications and the pricing of internet services , and other factors . the growth in internet traffic has a more significant impact on our net-centric customers who represent the vast majority of the traffic on our network and who tend to consume the majority of their allocated bandwidth on their connections . net-centric customers tend to purchase their service on a price per megabit basis . our corporate customers tend to utilize a small portion of their allocated bandwidth on their connections and tend to purchase their service on a per connection basis . we are a facilities-based provider of internet access and communications services . facilities-based providers require significant physical assets , or network facilities , to provide their services . typically when a facilities-based network services provider begins providing its services in a new jurisdiction losses are incurred for several years until economies of scale have been achieved . our foreign operations are in europe , canada , mexico and asia . europe accounts for roughly 80 % of our foreign operations . our european operations have incurred losses and will continue to do so until our european customer base and revenues have grown enough to achieve sufficient economies of scale . due to our strategic acquisitions of network assets and equipment , we believe we are well positioned to grow our revenue base . we continue to purchase and deploy network equipment to parts of our network to maximize the utilization of our assets and to expand and increase the capacity of our 29 network . our future capital expenditures will be based primarily on the expansion of our network and the addition of on-net buildings . we plan to continue to expand our network and to increase the number of on-net buildings we serve including multi-tenant office buildings and carrier neutral data centers . many factors can affect our ability to add buildings to our network . these factors include the willingness of building owners to grant us access rights , the availability of optical fiber networks to serve those buildings , the cost to connect buildings to our network and equipment availability . results of operations year ended december 31 , 2015 compared to the year ended december 31 , 2014 our management reviews and analyzes several key financial measures in order to manage our business and assess the quality of and variability of our service revenue , operating results and cash flows . the following summary tables present a comparison of our results of operations with respect to certain key financial measures . the comparisons illustrated in the tables are discussed in greater detail below . replace_table_token_5_th nmnot meaningful ( 1 ) includes non-cash equity-based compensation expense of $ 584 and $ 488 for 2015 and 2014 , respectively . story_separator_special_tag our increase in interest expense is attributed to interest expense related to the issuance of our $ 200.0 million of senior unsecured notes outstanding since april 9 , 2014 and interest expense related to the issuance of our $ 65.0 million of senior secured notes outstanding since august 19 , 2013 , partly offset by the decline of interest expense from our convertible notes that we repaid in june 2014. income tax ( expense ) benefit . our income tax benefit was $ 49.7 million for 2013 and our income tax expense was $ 3.7 million for 2014. the net income tax expense for 2014 includes united states federal income taxes of $ 2.5 million and state income taxes of $ 1.1 million . the net income tax benefit for 2013 includes income tax benefits of approximately $ 50.2 million resulting primarily from the reduction of the valuation allowance on net deferred tax assets related to our operations in the united states , and $ 0.5 million of income tax expense related to our european and canadian operations . at each balance sheet date , we assess the likelihood that we will be able to realize our deferred tax assets . we consider all available positive and negative evidence in assessing the 35 need for a valuation allowance . as of december 31 , 2013 , we recorded an income tax benefit of $ 50.2 million ( including $ 49.3 million related to our us federal deferred tax assets ) since we determined that we no longer required a valuation allowance against our us deferred tax assets . we continue to maintain a valuation allowance against our european and other foreign deferred tax assets and our deferred tax assets limited under section 382 of the internal revenue code in the united states . section 382 limits the utilization of net operating losses when ownership changes , as defined by that section , occur . we have performed an analysis of our section 382 ownership changes and we have determined that the utilization of certain of our net operating loss carryforwards in the united states is limited . our net operating losses related to our foreign operations are generally not subject to similar limitations . of the $ 390.6 million of net operating losses available at december 31 , 2014 in the united states approximately $ 286 million are unavailable for use and approximately $ 81 million are limited for use under section 382. our net operating loss carryforwards outside of the united states totaling approximately $ 789 million are not subject to limitations similar to section 382. buildings on-net . as of december 31 , 2014 and 2013 we had a total of 2,125 and 1,990 on-net buildings connected to our network , respectively . liquidity and capital resources in assessing our liquidity , management reviews and analyzes our current cash balances , short-term investments , accounts receivable , accounts payable , accrued liabilities , capital expenditure and operating expense commitments , and required capital lease , interest and debt payments and other obligations . the following table sets forth our consolidated cash flows . replace_table_token_9_th net cash provided by operating activities . our primary source of operating cash is receipts from our customers who are billed on a monthly basis for our services . our primary uses of operating cash are payments made to our vendors , employees and interest payments made to our capital lease vendors and our note holders . our changes in cash provided by operating activities are primarily due to changes in our operating profit and changes in our interest payments . cash provided by operating activities for 2015 , 2014 and 2013 includes interest payments on our note obligations of $ 29.3 million , $ 26.3 million and $ 15.6 million , respectively . story_separator_special_tag the funds from the escrow account ( such date of release , the `` escrow release date `` ) and to group after the escrow release date . as a condition to releasing the funds from escrow we redeemed our remaining outstanding convertible notes on june 20 , 2014 ( the `` redemption transaction `` ) . after consummation of the redemption transaction , cogent finance merged with group , with group continuing as the surviving corporation ( the `` finance merger `` ) . at the time of consummation of the finance merger , group assumed the obligations of cogent finance under the 2021 notes and the indenture governing the 2021 notes ( the `` indenture `` ) and group and each of group 's domestic subsidiaries became party to the indenture pursuant to a supplemental indenture to the indenture and the obligations under the indenture became obligations solely of group and each of group 's domestic subsidiaries . holdings also provided a guarantee of the 2021 notes but holdings is not subject to any of the covenants under the indenture . after the conditions to the release of the escrow proceeds were satisfied , on june 25 , 2014 ( the `` escrow release date `` ) the proceeds from the 2021 notes were released . the net proceeds from the offering were $ 195.8 million after deducting discounts and commissions and offering expenses . the net proceeds from the offering are intended to be used for general corporate purposes . the 2021 notes were issued pursuant to , and are governed by the indenture between cogent finance and the trustee . the 2021 notes bear interest at a rate of 5.625 % per year and will mature on april 15 , 2021. interest began to accrue on the 2021 notes on april 9 , 2014 and will be paid semi-annually on april 15 and october 15 , commencing on october 15 , 2014. following the escrow release date , the 2021 notes became group 's senior unsecured obligations and are guaranteed on a senior unsecured basis by the company . the 2021 notes are effectively subordinated

