we also generate revenue from fees charged to both clients and freelancers for other services , such as for transacting payments through our work marketplace , premium offerings , purchases of connects , foreign currency exchange , and our upwork payroll offering . in addition , we provide a managed services offering where we engage freelancers to complete projects , directly invoice the client , and assume responsibility for work performed . on december 31 , 2019 , we adopted topic 606 effective as of january 1 , 2019 using the modified retrospective method . as a result , revenue results for the years ended december 31 , 2020 and 2019 are presented in accordance with this new revenue recognition standard while historical revenue results for reporting periods prior to 2019 are presented in conformity with amounts previously disclosed under the prior revenue recognition standard , topic 605. financial highlights for 2020 in march 2020 , the world health organization declared the outbreak of covid-19 to be a pandemic , which continues to spread throughout the united states and the world , and has resulted in governmental authorities implementing numerous measures to contain the virus , including travel bans and restrictions , shelter-in-place orders , and business limitations and shutdowns . the covid-19 pandemic and the resulting restrictions intended to prevent its spread have accelerated the secular shift toward remote and independent work , and , with our unique , remote-based business model , the covid-19 pandemic has not impacted our clients ' access to highly-skilled freelancers to complete short- and long-term projects on our work marketplace . in 2020 , we continued to identify opportunities to prioritize our advertising and marketing efforts in order to reach those new and existing clients seeking to engage with independent talent due to the covid-19 pandemic , as well as companies that have already embraced a remote work model . as a result of these efforts , our 2020 results were fueled by both existing and new clients , who used our work marketplace to address their changing business needs . we began to see the impact of the pandemic on our results at the end of the first quarter , when we experienced a temporary reduction in the growth rates of gsv and revenue . this trend continued into the beginning of the second quarter , driven by spend contraction by many of our clients , as the covid-19 pandemic continued to disrupt their businesses . these trends stabilized in the second half of the second quarter , and improved thereafter , contributing to an overall increase in the growth 55 rates of gsv and revenue in 2020. also , beginning in the second half of the second quarter of 2020 , we began to see an increase in client acquisition driven by the acceleration in the shift toward remote work , due in part to the covid-19 pandemic and the execution of our strategic initiatives . this increase in client acquisition continued to accelerate in the second half of 2020 and drove an increase in freelancer billings , which , in turn , drove an increase in marketplace revenue . as a result , our work marketplace enabled $ 2.5 billion of gsv in 2020 , $ 2.1 billion in 2019 , and $ 1.8 billion in 2018 , representing year-over-year increases of 21 % in 2020 and 19 % in 2019. we generated revenue of $ 373.6 million in 2020 , $ 300.6 million in 2019 , and $ 253.4 million in 2018 , representing year-over-year increases of 24 % in 2020 and 19 % in 2019. while we have not incurred significant disruptions to our business thus far from the covid-19 pandemic , at this time , we are unable to fully assess the aggregate impact it will have on our business due to various uncertainties , which include , but are not limited to , the duration of the pandemic , its effect on the economy , its impact to the businesses of our clients , actions that may be taken by governmental authorities related to the pandemic , and other factors identified in part i , item 1a “ risk factors ” in this annual report , including the risk factor titled “ our business experienced , and may again experience , an adverse impact from the ongoing covid-19 pandemic . in addition , users may reduce their use of our work marketplace following the covid-19 pandemic . ” additionally , while we have made significant investments to grow our business , including investments in sales and marketing to acquire new clients and drive brand awareness , in the fourth quarter of 2020 , we decided that it was no longer cost-effective for our sales team to sell our upwork business offering . we do not expect this decision to have a material impact on our marketplace revenue , as we will service those clients that we had previously targeted with our upwork business offering with our other marketplace offerings , such as upwork basic and plus . in 2020 , we also made significant investments in research and development to build new product features and launch new offerings and in operations and personnel , and we intend to continue to focus on these efforts . as a result , we generated a net loss of $ 22.9 million in 2020 compared to a net loss of $ 16.7 million in 2019. our adjusted ebitda was $ 14.0 million in 2020 , an increase of 89 % from 2019. adjusted ebitda is a financial measure that is not prepared in accordance with , and is not an alternative to , financial measures prepared in accordance with u.s. gaap . see the section titled “ selected consolidated financial data—non-gaap financial measures ” for a definition of adjusted ebitda and information regarding our use of adjusted ebitda and a reconciliation of net loss to adjusted ebitda . story_separator_special_tag marketplace revenue , which represents the majority of our total revenue , is primarily comprised of the service fees paid by freelancers as a percentage of the total amount that freelancers charge clients for services accessed through our work marketplace and , to a lesser extent , payment processing and administration fees paid by clients . in the fourth quarter of 2020 , we decided that it was no longer cost-effective for our sales team to sell our upwork business offering . we do not expect this decision to have a material impact on our marketplace revenue , as we will service those clients that we had previously targeted with our upwork business offering with our other marketplace offerings , such as upwork basic and plus . our upwork basic and plus offerings provide clients with access to freelancers with verified work history and client feedback on our work marketplace , the ability to instantly match with the right freelancers , and built-in collaboration features . for freelancers working with clients that are on our upwork basic and plus offerings , we have a tiered freelancer service fee schedule based on cumulative lifetime billings by the freelancer to each client . freelancers typically pay us 20 % of the first $ 500 , 10 % for the next $ 9,500 , and then 5 % for any amount over $ 10,000 they bill to each client through our work marketplace . we recognize revenue on sunday for the majority of our tiered freelancer service fees each week . to a lesser extent , we also generate revenue from freelancers through membership fees , purchases of connects , and withdrawal and other fees . in addition , we generate marketplace revenue from our upwork basic and plus offerings by charging clients a payment processing and administration fee . clients using our upwork basic offering pay a fee equal to 3 % of their client spend . we recognize revenue on monday for a substantial portion of our client fees each week . clients using our upwork plus offering pay a flat fee of approximately $ 50 per month for additional features and pay a fee equal to 3 % of their client spend unless they pay via ach ( in which case , provided all eligibility criteria are met , the fee is waived ) . to a lesser extent , we also generate revenue from clients through foreign currency exchange fees when clients choose to pay in currencies other than the u.s. dollar . our upwork enterprise and other premium offerings , which are designed for larger clients , include access to additional product features , premium access to top freelancers , professional services , custom reporting , and flexible payment terms . for our upwork enterprise offering , we charge clients a monthly or annual subscription fee and a service fee calculated as a percentage of the client 's spend on freelancer services , in addition to the service fees paid by freelancers . additionally , upwork enterprise clients can also subscribe to a compliance offering that includes worker classification services for an additional fee and may also choose to use our work marketplace to engage freelancers that were not originally sourced through our work marketplace for a lower fee percentage . one of our premium offerings , upwork payroll , is available to clients when freelancers are classified as employees for engagements on our work marketplace . the client enters into an upwork payroll agreement with us , and we separately contract 59 with unrelated third-party staffing providers that provide employment services to such clients . revenue from upwork payroll is currently immaterial . the covid-19 pandemic and the resulting restrictions intended to prevent its spread have accelerated the secular shift toward remote and independent work . in 2020 , we continued to identify opportunities to prioritize our advertising and marketing efforts in order to reach those new and existing clients seeking to engage with independent talent due to the covid-19 pandemic , as well as companies that have already embraced a remote work model . as a result of these efforts , coupled with our execution against strategic initiatives , our 2020 results were fueled by both existing and new clients , who used our work marketplace to address their changing business needs and drove an increase in freelancer billings , which , in turn , drove an increase in marketplace revenue . although the covid-19 pandemic did not have a material adverse impact on our financial results for the year ended december 31 , 2020 , we are continuously evaluating the nature of and extent to which the covid-19 pandemic will impact our business , operating results , and financial condition . managed services revenue . through our managed services offering , we are responsible for providing services and engaging freelancers directly or as employees of third-party staffing providers to perform services for clients on our behalf . the freelancers providing services in connection with our managed services include independent talent and agencies of varying sizes . under u.s. gaap , we are deemed to be the principal in these managed services arrangements and therefore recognize the entire gsv of managed services projects as managed services revenue , as compared to recognizing only the percentage of the client spend that we receive , as we do with our marketplace offerings . managed services revenue grew at a slower rate than our marketplace revenue in 2020 compared to 2019 , and we anticipate this trend to continue , as we primarily focus on increasing client usage of and spend on our marketplace offerings . cost of revenue and gross profit cost of revenue . cost of revenue consists primarily of the cost of payment processing fees , amounts paid to freelancers to deliver services for clients under our managed services offering , personnel-related costs for our services and support personnel , third-party hosting fees for our use

cash flows the following table summarizes our cash flows for the years ended december 31 , 2020 , 2019 , and 2018 ( in thousands ) : replace_table_token_22_th operating activities our largest source of cash from operating activities is revenue generated from our work marketplace . our primary uses of cash from operating activities are for personnel-related expenditures , marketing activities , including advertising , payment processing fees , amounts paid to freelancers to deliver services for clients under our managed services offering , and third-party hosting costs . in addition , because we are licensed as an internet escrow agent , our total cash and cash provided by operating activities may be impacted by the timing of the end of our fiscal quarter as discussed in the section titled “ —liquidity and capital resources—escrow funding requirements. ” net cash provided by operating activities during 2020 was $ 22.4 million , which resulted from non-cash charges of $ 43.0 million and net cash inflows of $ 2.2 million from changes in operating assets and liabilities , offset by a net loss of $ 22.9 million . the change in operating assets and liabilities primarily resulted from changes in trade and client receivables , accrued expenses , and other current and long-term liabilities . due to fluctuations in revenue and the number of transactions on our work marketplace , coupled with fluctuations in the timing of cash receipts and payments , our operating assets and liabilities will likely continue to fluctuate in the future . net cash provided by operating activities during 2019 was $ 1.1 million , which resulted from non-cash charges of $ 32.2 million , offset by a net loss of $ 16.7 million and net cash outflows of $ 14.4 million from changes in operating assets and liabilities . the change in operating assets and liabilities primarily resulted from the increase in trade and client receivables of $ 10.9 million .


 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.
     ```cash flows the following table summarizes our cash flows for the years ended december 31 , 2020 , 2019 , and 2018 ( in thousands ) : replace_table_token_22_th operating activities our largest source of cash from operating activities is revenue generated from our work marketplace . our primary uses of cash from operating activities are for personnel-related expenditures , marketing activities , including advertising , payment processing fees , amounts paid to freelancers to deliver services for clients under our managed services offering , and third-party hosting costs . in addition , because we are licensed as an internet escrow agent , our total cash and cash provided by operating activities may be impacted by the timing of the end of our fiscal quarter as discussed in the section titled “ —liquidity and capital resources—escrow funding requirements. ” net cash provided by operating activities during 2020 was $ 22.4 million , which resulted from non-cash charges of $ 43.0 million and net cash inflows of $ 2.2 million from changes in operating assets and liabilities , offset by a net loss of $ 22.9 million . the change in operating assets and liabilities primarily resulted from changes in trade and client receivables , accrued expenses , and other current and long-term liabilities . due to fluctuations in revenue and the number of transactions on our work marketplace , coupled with fluctuations in the timing of cash receipts and payments , our operating assets and liabilities will likely continue to fluctuate in the future . net cash provided by operating activities during 2019 was $ 1.1 million , which resulted from non-cash charges of $ 32.2 million , offset by a net loss of $ 16.7 million and net cash outflows of $ 14.4 million from changes in operating assets and liabilities . the change in operating assets and liabilities primarily resulted from the increase in trade and client receivables of $ 10.9 million .
```    
 Suspicious Activity Report : we also generate revenue from fees charged to both clients and freelancers for other services , such as for transacting payments through our work marketplace , premium offerings , purchases of connects , foreign currency exchange , and our upwork payroll offering . in addition , we provide a managed services offering where we engage freelancers to complete projects , directly invoice the client , and assume responsibility for work performed . on december 31 , 2019 , we adopted topic 606 effective as of january 1 , 2019 using the modified retrospective method . as a result , revenue results for the years ended december 31 , 2020 and 2019 are presented in accordance with this new revenue recognition standard while historical revenue results for reporting periods prior to 2019 are presented in conformity with amounts previously disclosed under the prior revenue recognition standard , topic 605. financial highlights for 2020 in march 2020 , the world health organization declared the outbreak of covid-19 to be a pandemic , which continues to spread throughout the united states and the world , and has resulted in governmental authorities implementing numerous measures to contain the virus , including travel bans and restrictions , shelter-in-place orders , and business limitations and shutdowns . the covid-19 pandemic and the resulting restrictions intended to prevent its spread have accelerated the secular shift toward remote and independent work , and , with our unique , remote-based business model , the covid-19 pandemic has not impacted our clients ' access to highly-skilled freelancers to complete short- and long-term projects on our work marketplace . in 2020 , we continued to identify opportunities to prioritize our advertising and marketing efforts in order to reach those new and existing clients seeking to engage with independent talent due to the covid-19 pandemic , as well as companies that have already embraced a remote work model . as a result of these efforts , our 2020 results were fueled by both existing and new clients , who used our work marketplace to address their changing business needs . we began to see the impact of the pandemic on our results at the end of the first quarter , when we experienced a temporary reduction in the growth rates of gsv and revenue . this trend continued into the beginning of the second quarter , driven by spend contraction by many of our clients , as the covid-19 pandemic continued to disrupt their businesses . these trends stabilized in the second half of the second quarter , and improved thereafter , contributing to an overall increase in the growth 55 rates of gsv and revenue in 2020. also , beginning in the second half of the second quarter of 2020 , we began to see an increase in client acquisition driven by the acceleration in the shift toward remote work , due in part to the covid-19 pandemic and the execution of our strategic initiatives . this increase in client acquisition continued to accelerate in the second half of 2020 and drove an increase in freelancer billings , which , in turn , drove an increase in marketplace revenue . as a result , our work marketplace enabled $ 2.5 billion of gsv in 2020 , $ 2.1 billion in 2019 , and $ 1.8 billion in 2018 , representing year-over-year increases of 21 % in 2020 and 19 % in 2019. we generated revenue of $ 373.6 million in 2020 , $ 300.6 million in 2019 , and $ 253.4 million in 2018 , representing year-over-year increases of 24 % in 2020 and 19 % in 2019. while we have not incurred significant disruptions to our business thus far from the covid-19 pandemic , at this time , we are unable to fully assess the aggregate impact it will have on our business due to various uncertainties , which include , but are not limited to , the duration of the pandemic , its effect on the economy , its impact to the businesses of our clients , actions that may be taken by governmental authorities related to the pandemic , and other factors identified in part i , item 1a “ risk factors ” in this annual report , including the risk factor titled “ our business experienced , and may again experience , an adverse impact from the ongoing covid-19 pandemic . in addition , users may reduce their use of our work marketplace following the covid-19 pandemic . ” additionally , while we have made significant investments to grow our business , including investments in sales and marketing to acquire new clients and drive brand awareness , in the fourth quarter of 2020 , we decided that it was no longer cost-effective for our sales team to sell our upwork business offering . we do not expect this decision to have a material impact on our marketplace revenue , as we will service those clients that we had previously targeted with our upwork business offering with our other marketplace offerings , such as upwork basic and plus . in 2020 , we also made significant investments in research and development to build new product features and launch new offerings and in operations and personnel , and we intend to continue to focus on these efforts . as a result , we generated a net loss of $ 22.9 million in 2020 compared to a net loss of $ 16.7 million in 2019. our adjusted ebitda was $ 14.0 million in 2020 , an increase of 89 % from 2019. adjusted ebitda is a financial measure that is not prepared in accordance with , and is not an alternative to , financial measures prepared in accordance with u.s. gaap . see the section titled “ selected consolidated financial data—non-gaap financial measures ” for a definition of adjusted ebitda and information regarding our use of adjusted ebitda and a reconciliation of net loss to adjusted ebitda . story_separator_special_tag marketplace revenue , which represents the majority of our total revenue , is primarily comprised of the service fees paid by freelancers as a percentage of the total amount that freelancers charge clients for services accessed through our work marketplace and , to a lesser extent , payment processing and administration fees paid by clients . in the fourth quarter of 2020 , we decided that it was no longer cost-effective for our sales team to sell our upwork business offering . we do not expect this decision to have a material impact on our marketplace revenue , as we will service those clients that we had previously targeted with our upwork business offering with our other marketplace offerings , such as upwork basic and plus . our upwork basic and plus offerings provide clients with access to freelancers with verified work history and client feedback on our work marketplace , the ability to instantly match with the right freelancers , and built-in collaboration features . for freelancers working with clients that are on our upwork basic and plus offerings , we have a tiered freelancer service fee schedule based on cumulative lifetime billings by the freelancer to each client . freelancers typically pay us 20 % of the first $ 500 , 10 % for the next $ 9,500 , and then 5 % for any amount over $ 10,000 they bill to each client through our work marketplace . we recognize revenue on sunday for the majority of our tiered freelancer service fees each week . to a lesser extent , we also generate revenue from freelancers through membership fees , purchases of connects , and withdrawal and other fees . in addition , we generate marketplace revenue from our upwork basic and plus offerings by charging clients a payment processing and administration fee . clients using our upwork basic offering pay a fee equal to 3 % of their client spend . we recognize revenue on monday for a substantial portion of our client fees each week . clients using our upwork plus offering pay a flat fee of approximately $ 50 per month for additional features and pay a fee equal to 3 % of their client spend unless they pay via ach ( in which case , provided all eligibility criteria are met , the fee is waived ) . to a lesser extent , we also generate revenue from clients through foreign currency exchange fees when clients choose to pay in currencies other than the u.s. dollar . our upwork enterprise and other premium offerings , which are designed for larger clients , include access to additional product features , premium access to top freelancers , professional services , custom reporting , and flexible payment terms . for our upwork enterprise offering , we charge clients a monthly or annual subscription fee and a service fee calculated as a percentage of the client 's spend on freelancer services , in addition to the service fees paid by freelancers . additionally , upwork enterprise clients can also subscribe to a compliance offering that includes worker classification services for an additional fee and may also choose to use our work marketplace to engage freelancers that were not originally sourced through our work marketplace for a lower fee percentage . one of our premium offerings , upwork payroll , is available to clients when freelancers are classified as employees for engagements on our work marketplace . the client enters into an upwork payroll agreement with us , and we separately contract 59 with unrelated third-party staffing providers that provide employment services to such clients . revenue from upwork payroll is currently immaterial . the covid-19 pandemic and the resulting restrictions intended to prevent its spread have accelerated the secular shift toward remote and independent work . in 2020 , we continued to identify opportunities to prioritize our advertising and marketing efforts in order to reach those new and existing clients seeking to engage with independent talent due to the covid-19 pandemic , as well as companies that have already embraced a remote work model . as a result of these efforts , coupled with our execution against strategic initiatives , our 2020 results were fueled by both existing and new clients , who used our work marketplace to address their changing business needs and drove an increase in freelancer billings , which , in turn , drove an increase in marketplace revenue . although the covid-19 pandemic did not have a material adverse impact on our financial results for the year ended december 31 , 2020 , we are continuously evaluating the nature of and extent to which the covid-19 pandemic will impact our business , operating results , and financial condition . managed services revenue . through our managed services offering , we are responsible for providing services and engaging freelancers directly or as employees of third-party staffing providers to perform services for clients on our behalf . the freelancers providing services in connection with our managed services include independent talent and agencies of varying sizes . under u.s. gaap , we are deemed to be the principal in these managed services arrangements and therefore recognize the entire gsv of managed services projects as managed services revenue , as compared to recognizing only the percentage of the client spend that we receive , as we do with our marketplace offerings . managed services revenue grew at a slower rate than our marketplace revenue in 2020 compared to 2019 , and we anticipate this trend to continue , as we primarily focus on increasing client usage of and spend on our marketplace offerings . cost of revenue and gross profit cost of revenue . cost of revenue consists primarily of the cost of payment processing fees , amounts paid to freelancers to deliver services for clients under our managed services offering , personnel-related costs for our services and support personnel , third-party hosting fees for our use

