we view our average monthly unique users as a key indicator of the quality of our user experience , the effectiveness of our advertising and traffic acquisition , and the strength of our brand awareness . measuring unique users is important to us because our marketplace subscription revenue depends , in part , on our ability to provide dealers with connections to our users and exposure to our marketplace audience . we define connections as interactions between consumers and dealers on our marketplace through phone calls , email , managed text and chat , and clicks to access the dealer 's website or map directions to the dealership . replace_table_token_4_th monthly sessions we define monthly sessions as the number of distinct visits to our websites that take place each month within a given time frame , as measured and defined by google analytics . we calculate average monthly sessions as the sum of the monthly sessions in a given period , divided by the number of months in that period . a session is defined as beginning with the first page view from a computer or mobile device and ending at the earliest of when a user closes their browser window , after 30 minutes of inactivity , or at midnight eastern time each night . a session can be made up of multiple page views and visitor actions , such as performing a search , visiting vehicle detail pages , and connecting with a dealer . we believe the volume of sessions in a time period , when considered in conjunction with the number of unique users in that time period , is an indicator of consumer satisfaction and engagement with our marketplace . replace_table_token_5_th number of paying dealers a paying dealer is a dealer , based on a distinct associated inventory feed , that subscribes to our enhanced or featured listing product at the end of a defined period . we believe that the number of paying dealers is indicative of the value proposition of our listing products , and our sales and marketing success , including our ability to retain paying dealers and develop new dealer relationships . replace_table_token_6_th 40 average annual revenue per subscribing dealer ( aarsd ) we measure the average annual revenue we receive from each paying dealer . we define aarsd , which is measured at the end of a defined period , as the total marketplace subscription revenue during the trailing 12 months divided by the average number of paying dealers during the same trailing 12-month period . we believe that our ability to grow aarsd is an indicator of the value proposition of our products and the return on investment , or roi , our paying dealers realize from our products . increases in aarsd , which we believe reflect the value of exposure to our engaged audience in relation to subscription cost , are driven by our ability to grow the volume of connections to our users and the quality of those connections , which result in increased opportunity to upsell package levels and cross-sell additional products to our paying dealers . replace_table_token_7_th adjusted ebitda we define adjusted ebitda as net income ( loss ) , adjusted to exclude : depreciation and amortization , stock‑based compensation expense , other ( income ) expense , net , the ( benefit from ) provision for income taxes , and certain one‑time , non‑recurring items , if and when applicable . we monitor and have presented adjusted ebitda in this annual report on form 10-k as a non‑gaap financial measure to supplement the financial information we present on a gaap basis to provide investors with additional information regarding our financial results . adjusted ebitda , as a non‑gaap financial measure , should not be considered in isolation from , or as an alternative to , measures prepared in accordance with gaap . we consider , and you should consider , adjusted ebitda together with other operating and financial performance measures presented in accordance with gaap . also , our non‑gaap measure may not necessarily be comparable to similarly titled measures presented by other companies . we believe that adjusted ebitda is a key indicator of our operating results . for further explanation of the uses and limitations of this measure and a reconciliation of our adjusted ebitda to the most directly comparable gaap measure , net income , please see “ selected consolidated financial data — adjusted ebitda . ” components of consolidated statements of operations revenue our revenue is derived from two primary sources : ( i ) marketplace subscription revenue and ( ii ) advertising and other revenue , as described below . marketplace subscription revenue we offer three types of marketplace listing products to dealers : basic listing , which is free ; and enhanced or featured listing , which require a paid subscription under a monthly , quarterly , semiannual , or annual subscription basis . contractual subscriptions for customers generally auto‑renew on a monthly basis and are cancellable by dealers with 30‑days ' advance notice . we also offer listing dealers access to the dealer dashboard , which includes a performance summary , dealer insights tool , user review management platform , pricing tool , and market analysis tool . the pricing tool and market analysis tool are available only to paying dealers . in addition to listing inventory in the marketplace and providing access to the dealer dashboard , we offer enhanced and featured listing dealers other subscription advertising and customer acquisition products , including display advertising that appears in our marketplace and on other sites on the internet . this advertising can be targeted by geography , search history , and a number of other factors , and dealer search engine marketing , which helps dealers more effectively acquire customers through paid search , social media , and retargeted advertising . story_separator_special_tag $ 0.9 million increase in costs to improve the content on our websites , a $ 0.8 million increase for data center and hosting costs , and a $ 0.5 million increase in amortization of website development costs . operating expenses sales and marketing expenses replace_table_token_25_th sales and marketing expenses increased $ 82.0 million , or 53 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. this increase was due primarily to an increase in advertising costs of $ 61.0 million , a $ 12.8 million increase in salaries , commissions , and related expenses due to our increased revenue and a 21 % increase in headcount , a $ 2.0 million increase in expenses related to marketing events and activities , a $ 1.7 million increase in consulting fees , a $ 1.0 million increase in rent due to the expansion of our office space , and a $ 0.8 million increase in software subscriptions . the increase for the year ended december 31 , 2017 was also due to a $ 1.7 million increase in stock-based compensation expense primarily due to the recognition of expense related to rsus with a performance condition satisfied on the effectiveness of the registration statement for our ipo . although the performance-based vesting condition was satisfied , under the terms of the awards , the settlement of such vested rsus and the issuance of common stock with respect to such vested rsus will occur on april 10 , 2018 , one hundred eighty-one days after the satisfaction of the performance condition . product , technology , and development expenses replace_table_token_26_th 50 product , technology , and development expenses increased $ 11.0 million , or 96 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016 . the increase was due primarily to an increase in salar ies and related employment expenses due to a 68 % increase in headcount to support our growth and product innovations . the increase for the year ended december 31 , 2017 was also due to a $ 1.7 million increase in stock-based compensation expense primarily du e to the recognition of expense related to rsus with a performance condition satisfied on the effectiveness of the registration statement for our ipo . general and administrative expenses replace_table_token_27_th general and administrative expenses increased $ 9.9 million , or 77 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. the change primarily reflected an increase of $ 5.0 million of salaries and employee-related costs as a result of our 81 % increase in headcount as we continued to grow our business and require additional personnel to support our expanded operations , a $ 1.4 million increase in payment processing and billing costs due to increased customer transactions with higher billings , a $ 1.1 million increase in external consulting and insurance fees driven by costs incurred to comply with public company requirements , and a $ 0.6 million increase in bad debt expense . the increase for the year ended december 31 , 2017 was also due to a $ 1.3 million increase in stock-based compensation expense primarily due to the recognition of expense related to rsus with a performance condition satisfied on the effectiveness of the registration statement for our ipo . depreciation and amortization expenses replace_table_token_28_th depreciation and amortization expenses increased $ 1.0 million , or 62 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016 , due primarily to increased depreciation of additional leasehold improvements . other income , net replace_table_token_29_th 51 other income , net increased $ 0.2 million , or 51 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. the $ 0.5 million increase in interest income is primarily due to the investment of cash in certificates of deposit and money market funds arising from our increased cash from operations and the funds raised in ou r ipo . the $ 0.3 million de crease in other income ( expense ) is primarily due to losses on foreign currency transactions , primarily a result of the u.s. dollar weakening against the euro . provision for income taxes replace_table_token_30_th the provision for income taxes increased $ 0.2 million , or 8 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. in 2017 , we recorded a tax provision on earnings with an effective tax rate of 16.7 % compared to 27.4 % in 2016. our lower effective tax rate during 2017 is primarily the result of discrete items recorded including ipo deductible costs and higher excess tax deductions relating to stock-based compensation awards . our lower effective tax rate during 2017 was also driven by higher r & d tax credits . income ( loss ) from operations by segment replace_table_token_31_th nm — not meaningful u.s. income from operations increased $ 14.1 million , or 51 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. this increase was due to an increase in revenue of $ 111.6 million , offset in part by the increases in cost of revenue of $ 6.5 million and operating expenses of $ 91.0 million . international loss from operations increased $ 7.4 million in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. the increase in international loss from operations reflects our continued investment into international markets and expansion into new countries . liquidity and capital resources cash , cash equivalents and investments at december 31 , 2018 and 2017 , our principal sources of liquidity were cash and cash equivalents of $ 34.9 million and $ 87.7 million , respectively and investments

sources and uses of cash our cash flows from operating , investing , and financing activities , as reflected in the consolidated statements of cash flows , are summarized in the following table : replace_table_token_32_th our operations have been financed primarily from operating activities , sales of preferred stock and our ipo . we generated cash from operating activities of $ 51.7 million during 2018 , $ 25.7 million during 2017 and $ 20.0 million during 2016 , and we expect to generate cash from operations for the foreseeable future . we believe that our existing sources of liquidity will be sufficient to fund our operations for at least the next 12 months from the date of the filing of this annual report on form 10-k. however , our future capital requirements will depend on many factors , including our rate of revenue growth , the expansion of our sales and marketing activities , the support of our product , technology , and development efforts , and the timing and extent of our investment in international markets . to the extent that existing cash , cash equivalents , and investments and cash from operations are insufficient to fund our future activities , we may need to raise additional funds through public or private equity or debt financing . additional funds may not be available on terms favorable to us , or at all .


 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.
     ```sources and uses of cash our cash flows from operating , investing , and financing activities , as reflected in the consolidated statements of cash flows , are summarized in the following table : replace_table_token_32_th our operations have been financed primarily from operating activities , sales of preferred stock and our ipo . we generated cash from operating activities of $ 51.7 million during 2018 , $ 25.7 million during 2017 and $ 20.0 million during 2016 , and we expect to generate cash from operations for the foreseeable future . we believe that our existing sources of liquidity will be sufficient to fund our operations for at least the next 12 months from the date of the filing of this annual report on form 10-k. however , our future capital requirements will depend on many factors , including our rate of revenue growth , the expansion of our sales and marketing activities , the support of our product , technology , and development efforts , and the timing and extent of our investment in international markets . to the extent that existing cash , cash equivalents , and investments and cash from operations are insufficient to fund our future activities , we may need to raise additional funds through public or private equity or debt financing . additional funds may not be available on terms favorable to us , or at all .
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 Suspicious Activity Report : we view our average monthly unique users as a key indicator of the quality of our user experience , the effectiveness of our advertising and traffic acquisition , and the strength of our brand awareness . measuring unique users is important to us because our marketplace subscription revenue depends , in part , on our ability to provide dealers with connections to our users and exposure to our marketplace audience . we define connections as interactions between consumers and dealers on our marketplace through phone calls , email , managed text and chat , and clicks to access the dealer 's website or map directions to the dealership . replace_table_token_4_th monthly sessions we define monthly sessions as the number of distinct visits to our websites that take place each month within a given time frame , as measured and defined by google analytics . we calculate average monthly sessions as the sum of the monthly sessions in a given period , divided by the number of months in that period . a session is defined as beginning with the first page view from a computer or mobile device and ending at the earliest of when a user closes their browser window , after 30 minutes of inactivity , or at midnight eastern time each night . a session can be made up of multiple page views and visitor actions , such as performing a search , visiting vehicle detail pages , and connecting with a dealer . we believe the volume of sessions in a time period , when considered in conjunction with the number of unique users in that time period , is an indicator of consumer satisfaction and engagement with our marketplace . replace_table_token_5_th number of paying dealers a paying dealer is a dealer , based on a distinct associated inventory feed , that subscribes to our enhanced or featured listing product at the end of a defined period . we believe that the number of paying dealers is indicative of the value proposition of our listing products , and our sales and marketing success , including our ability to retain paying dealers and develop new dealer relationships . replace_table_token_6_th 40 average annual revenue per subscribing dealer ( aarsd ) we measure the average annual revenue we receive from each paying dealer . we define aarsd , which is measured at the end of a defined period , as the total marketplace subscription revenue during the trailing 12 months divided by the average number of paying dealers during the same trailing 12-month period . we believe that our ability to grow aarsd is an indicator of the value proposition of our products and the return on investment , or roi , our paying dealers realize from our products . increases in aarsd , which we believe reflect the value of exposure to our engaged audience in relation to subscription cost , are driven by our ability to grow the volume of connections to our users and the quality of those connections , which result in increased opportunity to upsell package levels and cross-sell additional products to our paying dealers . replace_table_token_7_th adjusted ebitda we define adjusted ebitda as net income ( loss ) , adjusted to exclude : depreciation and amortization , stock‑based compensation expense , other ( income ) expense , net , the ( benefit from ) provision for income taxes , and certain one‑time , non‑recurring items , if and when applicable . we monitor and have presented adjusted ebitda in this annual report on form 10-k as a non‑gaap financial measure to supplement the financial information we present on a gaap basis to provide investors with additional information regarding our financial results . adjusted ebitda , as a non‑gaap financial measure , should not be considered in isolation from , or as an alternative to , measures prepared in accordance with gaap . we consider , and you should consider , adjusted ebitda together with other operating and financial performance measures presented in accordance with gaap . also , our non‑gaap measure may not necessarily be comparable to similarly titled measures presented by other companies . we believe that adjusted ebitda is a key indicator of our operating results . for further explanation of the uses and limitations of this measure and a reconciliation of our adjusted ebitda to the most directly comparable gaap measure , net income , please see “ selected consolidated financial data — adjusted ebitda . ” components of consolidated statements of operations revenue our revenue is derived from two primary sources : ( i ) marketplace subscription revenue and ( ii ) advertising and other revenue , as described below . marketplace subscription revenue we offer three types of marketplace listing products to dealers : basic listing , which is free ; and enhanced or featured listing , which require a paid subscription under a monthly , quarterly , semiannual , or annual subscription basis . contractual subscriptions for customers generally auto‑renew on a monthly basis and are cancellable by dealers with 30‑days ' advance notice . we also offer listing dealers access to the dealer dashboard , which includes a performance summary , dealer insights tool , user review management platform , pricing tool , and market analysis tool . the pricing tool and market analysis tool are available only to paying dealers . in addition to listing inventory in the marketplace and providing access to the dealer dashboard , we offer enhanced and featured listing dealers other subscription advertising and customer acquisition products , including display advertising that appears in our marketplace and on other sites on the internet . this advertising can be targeted by geography , search history , and a number of other factors , and dealer search engine marketing , which helps dealers more effectively acquire customers through paid search , social media , and retargeted advertising . story_separator_special_tag $ 0.9 million increase in costs to improve the content on our websites , a $ 0.8 million increase for data center and hosting costs , and a $ 0.5 million increase in amortization of website development costs . operating expenses sales and marketing expenses replace_table_token_25_th sales and marketing expenses increased $ 82.0 million , or 53 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. this increase was due primarily to an increase in advertising costs of $ 61.0 million , a $ 12.8 million increase in salaries , commissions , and related expenses due to our increased revenue and a 21 % increase in headcount , a $ 2.0 million increase in expenses related to marketing events and activities , a $ 1.7 million increase in consulting fees , a $ 1.0 million increase in rent due to the expansion of our office space , and a $ 0.8 million increase in software subscriptions . the increase for the year ended december 31 , 2017 was also due to a $ 1.7 million increase in stock-based compensation expense primarily due to the recognition of expense related to rsus with a performance condition satisfied on the effectiveness of the registration statement for our ipo . although the performance-based vesting condition was satisfied , under the terms of the awards , the settlement of such vested rsus and the issuance of common stock with respect to such vested rsus will occur on april 10 , 2018 , one hundred eighty-one days after the satisfaction of the performance condition . product , technology , and development expenses replace_table_token_26_th 50 product , technology , and development expenses increased $ 11.0 million , or 96 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016 . the increase was due primarily to an increase in salar ies and related employment expenses due to a 68 % increase in headcount to support our growth and product innovations . the increase for the year ended december 31 , 2017 was also due to a $ 1.7 million increase in stock-based compensation expense primarily du e to the recognition of expense related to rsus with a performance condition satisfied on the effectiveness of the registration statement for our ipo . general and administrative expenses replace_table_token_27_th general and administrative expenses increased $ 9.9 million , or 77 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. the change primarily reflected an increase of $ 5.0 million of salaries and employee-related costs as a result of our 81 % increase in headcount as we continued to grow our business and require additional personnel to support our expanded operations , a $ 1.4 million increase in payment processing and billing costs due to increased customer transactions with higher billings , a $ 1.1 million increase in external consulting and insurance fees driven by costs incurred to comply with public company requirements , and a $ 0.6 million increase in bad debt expense . the increase for the year ended december 31 , 2017 was also due to a $ 1.3 million increase in stock-based compensation expense primarily due to the recognition of expense related to rsus with a performance condition satisfied on the effectiveness of the registration statement for our ipo . depreciation and amortization expenses replace_table_token_28_th depreciation and amortization expenses increased $ 1.0 million , or 62 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016 , due primarily to increased depreciation of additional leasehold improvements . other income , net replace_table_token_29_th 51 other income , net increased $ 0.2 million , or 51 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. the $ 0.5 million increase in interest income is primarily due to the investment of cash in certificates of deposit and money market funds arising from our increased cash from operations and the funds raised in ou r ipo . the $ 0.3 million de crease in other income ( expense ) is primarily due to losses on foreign currency transactions , primarily a result of the u.s. dollar weakening against the euro . provision for income taxes replace_table_token_30_th the provision for income taxes increased $ 0.2 million , or 8 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. in 2017 , we recorded a tax provision on earnings with an effective tax rate of 16.7 % compared to 27.4 % in 2016. our lower effective tax rate during 2017 is primarily the result of discrete items recorded including ipo deductible costs and higher excess tax deductions relating to stock-based compensation awards . our lower effective tax rate during 2017 was also driven by higher r & d tax credits . income ( loss ) from operations by segment replace_table_token_31_th nm — not meaningful u.s. income from operations increased $ 14.1 million , or 51 % , in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. this increase was due to an increase in revenue of $ 111.6 million , offset in part by the increases in cost of revenue of $ 6.5 million and operating expenses of $ 91.0 million . international loss from operations increased $ 7.4 million in the year ended december 31 , 2017 compared to the year ended december 31 , 2016. the increase in international loss from operations reflects our continued investment into international markets and expansion into new countries . liquidity and capital resources cash , cash equivalents and investments at december 31 , 2018 and 2017 , our principal sources of liquidity were cash and cash equivalents of $ 34.9 million and $ 87.7 million , respectively and investments

