the ongoing covid-19 surge , coupled alongside vaccine rollout logistics , likely indicate that our country and national healthcare system will be under some amount of continued strain over the coming months . that said , we continue to be encouraged as we witness meaningful evidence that the healthcare provider ecosystem is significantly better equipped and prepared to respond to the ongoing pandemic , including through its treatment efficacy , supply chain logistics , capacity planning , and broader operational optimization . lastly , we see additional reasons for optimism over the near-to-medium term , as we begin to witness early signs of progress on vaccine rollout logistics . we are fortunate to have a highly recurring revenue model in which greater than 90 % of our revenue is recurring in nature . as such , we expect that the near-term impact of covid-19 on our total revenue will be relatively muted , as evidenced by our revenue performance for the year ended december 31 , 2020. additionally , we benefit from a high level of technology revenue predictability , especially our dos subscription customers that typically have built-in , contractual technology revenue escalators . we also have developed a number of technology and services solutions designed specifically to support healthcare providers during the covid-19 pandemic . importantly , since the onset of the covid-19 pandemic , our customers ' overall usage of our data platform has increased meaningfully . additionally , we have seen usage of our covid-19-specific products shift from those focused on covid-19 preparedness to those focused on financial recovery and planning analytics in areas such as elective procedures , ambulatory care , and revenue cycle . given these factors , we have seen minimal impact on our technology dollar-based retention as a result of covid-19 and would anticipate similar dynamics moving forward . regarding our professional services , we continue to see high levels of engagement of our team member base , who remain engaged on both covid-19-recovery work as well as focusing on more general clinical , financial , and operational improvement work . that said , the financial strain imposed by covid-19 on a number of our customers has led to a meaningfully lower professional services dollar-based retention than we have achieved historically . the primary drivers for the decrease in our adjusted professional services gross margin from 35 % for the year ended december 31 , 2019 to 25 % for the year ended december 31 , 2020 include the lower professional services dollar-based retention mentioned above , temporary professional services discounts provided to support our customers through the near-term financial strain they have experienced related to covid-19 , as well as some shift in the mix of professional services delivered . we added nine net new dos subscription customers during the year ended december 31 , 2020. in the first half of 2020 , given the significant impact of covid-19 on our healthcare provider end market , the number of first half new customer additions was meaningfully lower than we originally anticipated entering the year . as we entered the second half of 2020 , we were pleased to see healthcare organizations adjusting well to the `` new normal `` operating environment , with covid-19 highlighting the need for a more robust , commercial-grade data and analytics solution . likewise , given the financial strain imposed by the pandemic , prospective customers have shown an increased focus on revenue and cost optimization analytics , from which we believe we are well positioned to benefit . on the other hand , the covid-19 pandemic continued to create some near-term financial uncertainty , making some health systems more cautious in their near-term purchasing decisions . given these operating dynamics , in the second half of 2020 we experienced similar overall pipeline conversion rates to the second half of 2019. any negative impact to 2020 total revenue caused by the covid-19 pandemic has also resulted in a negative impact to our 2020 adjusted ebitda . we have and continue to plan to partially offset any negative total revenue impact through cost containment efforts , resulting in less of a negative adjusted ebitda impact compared to the negative total revenue impact . importantly , in our response to the covid-19 pandemic , we remain centrally committed to our team members , ensuring they stay at the center of the health catalyst flywheel . as such , any cost containment efforts implemented will have a bias towards non-headcount related items . over the long run , as we get through the covid-19 pandemic and healthcare organizations ' operations begin to normalize , we continue to be optimistic that the pandemic will serve as an overall tailwind in the industry 's adoption of data and analytics . at the health system level , we are seeing meaningful evidence that covid-19 is highlighting the need for a commercial-grade data and analytics solution to replace patchwork homegrown systems . 62 our business model we offer our solution to a variety of healthcare organizations , primarily in the united states , including academic medical centers , integrated delivery networks , community hospitals , large physician practices , acos , health information exchanges , health insurers , and other risk-bearing entities . we categorize our customer count into two primary categories : dos subscription customers and other customers . dos subscription customers are defined as customers who access our dos platform via a technology subscription contract . other customers generally include dos non-subscription customers and other customers from historical acquisitions . as of december 31 , 2020 , 2019 , and 2018 , we had 74 , 65 , and 50 dos subscription customers with active subscriptions , respectively . story_separator_special_tag components of our results of operations revenue we derive our revenue from sales of technology and professional services . for the years ended december 31 , 2020 , 2019 , and 2018 , technology revenue represented 58 % , 54 % , and 51 % of total revenue , respectively , and professional services revenue represented 42 % , 46 % , and 49 % of total revenue , respectively . technology revenue . technology revenue primarily consists of subscription fees charged to customers for access to use our data platform and analytics applications . we provide customers access to our technology through either an all-access or limited-access , modular subscription . most of our subscription contracts are cloud-based and have up to a three-year term , of which the vast majority are terminable after one year upon 90 days ' notice . dos subscription customers that access our technology through an all-access or limited access , modular subscription generally have agreements with built-in annual escalators for technology access fees . also included in technology revenue is the maintenance and support we provide , which generally includes updates and support services . professional services revenue . professional services revenue primarily includes analytics services , domain expertise services , outsourcing services , and implementation services . professional services arrangements typically include a fee for making full-time equivalent ( fte ) services available to our customers on a monthly basis . fte services generally consist of a blend of analytic engineers , analysts , and data scientists based on the domain expertise needed to best serve our customers . 67 deferred revenue deferred revenue consists of customer billings in advance of revenue being recognized from our technology and professional services arrangements . we primarily invoice our customers for technology arrangements annually or quarterly in advance . amounts anticipated to be recognized within one year of the balance sheet date are recorded as deferred revenue and the remaining portion is recorded as deferred revenue , net of current portion on the consolidated balance sheets . cost of revenue , excluding depreciation and amortization cost of technology revenue . cost of technology revenue primarily consists of costs associated with hosting and supporting our technology , including third-party cloud computing and hosting costs , contractor costs , and salary and related personnel costs for our cloud services and support teams . although we expect cost of technology revenue to increase in absolute dollars as we transition customers to third-party hosted data centers with microsoft azure and increase headcount to accommodate growth , we anticipate cost of technology revenue as a percentage of technology revenue will generally decrease over the long term . we expect cost of technology revenue as a percentage of technology revenue to fluctuate and potentially increase in the near term , primarily due to additional costs associated with transitioning customers from on-premise and our managed data centers to microsoft azure . cost of professional services revenue . cost of professional services revenue consists primarily of costs related to delivering our team 's expertise in analytics , strategic advisory , improvement , and implementation services . these costs primarily include salary and related personnel costs , travel-related costs , and outside contractor costs . we expect cost of professional services revenue to increase in absolute dollars as we increase headcount to accommodate growth . operating expense sales and marketing . sales and marketing expenses primarily include salary and related personnel costs for our sales , marketing , and account management teams , lead generation , marketing events , including our healthcare analytics summit ( has ) , marketing programs , and outside contractor costs associated with the sale and marketing of our offerings . we plan to continue to invest in sales and marketing to grow our customer base , expand in new markets , and increase our brand awareness . the trend and timing of sales and marketing expenses will depend in part on the timing of our expansion into new markets and marketing campaigns . we expect that sales and marketing expenses will increase in absolute dollars in future periods , but decrease as a percentage of our revenue over the long term . our sales and marketing expenses may fluctuate as a percentage of our revenue from period to period due to the timing and extent of these expenses . research and development . research and development expenses primarily include salary and related personnel costs for our data platform and analytics applications teams , subscriptions , and outside contractor costs associated with the development of products . we have developed an open , flexible , and scalable data platform . we plan to continue to invest in research and development to develop new solutions and enhance our applications library . we expect that research and development expenses will increase in absolute dollars in future periods , but decrease as a percentage of our revenue over the long term . our research and development expenses may fluctuate as a percentage of our revenue from period to period due to the timing and extent of these expenses . general and administrative . general and administrative expenses primarily include salary and related personnel costs for our legal , finance , people operations , it , and other administrative teams , including certain executives . general and administrative expenses also include facilities , subscriptions , corporate insurance , outside legal , accounting , and directors ' fees . due to the closing of our ipo on july 29 , 2019 , we incurred and expect to continue to incur additional costs as a result of operating as a public company , including costs related to compliance and reporting obligations of public companies , and increased costs for insurance , investor relations , and corporate governance . as a result , we expect our general and administrative expenses to increase in absolute dollars for the foreseeable future , but decrease as a percentage of our

cash flows the following table summarizes our cash flows for the years ended december 31 , 2020 , 2019 , and 2018 : replace_table_token_29_th operating activities our largest source of operating cash flows is cash collections from our customers for technology and professional services arrangements . our primary uses of cash from operating activities are for employee-related expenses , marketing expenses , and technology costs . for the year ended december 31 , 2020 , net cash used in operating activities was $ 26.1 million , which included a net loss of $ 115.0 million . non-cash charges primarily consisted of $ 18.7 million in depreciation and amortization of property , equipment , and intangible assets , $ 38.0 million in stock-based compensation , $ 14.1 million in change in fair value of contingent consideration liabilities , $ 8.5 million of loss from the extinguishment of debt , and $ 8.1 million in amortization of debt discount and issuance costs . for the year ended december 31 , 2019 , net cash used in operating activities was $ 32.2 million , which included a net loss of $ 60.1 million . non-cash charges primarily consisted of $ 9.2 million in depreciation and amortization of property , equipment , and intangible assets , $ 17.8 million in stock-based compensation , $ 1.7 million of loss from the extinguishment of debt , and $ 1.1 million in amortization of debt discount and issuance costs . 77 for the year ended december 31 , 2018 , net cash used in operating activities was $ 40.3 million , which included a net loss of $ 62.0 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 : replace_table_token_29_th operating activities our largest source of operating cash flows is cash collections from our customers for technology and professional services arrangements . our primary uses of cash from operating activities are for employee-related expenses , marketing expenses , and technology costs . for the year ended december 31 , 2020 , net cash used in operating activities was $ 26.1 million , which included a net loss of $ 115.0 million . non-cash charges primarily consisted of $ 18.7 million in depreciation and amortization of property , equipment , and intangible assets , $ 38.0 million in stock-based compensation , $ 14.1 million in change in fair value of contingent consideration liabilities , $ 8.5 million of loss from the extinguishment of debt , and $ 8.1 million in amortization of debt discount and issuance costs . for the year ended december 31 , 2019 , net cash used in operating activities was $ 32.2 million , which included a net loss of $ 60.1 million . non-cash charges primarily consisted of $ 9.2 million in depreciation and amortization of property , equipment , and intangible assets , $ 17.8 million in stock-based compensation , $ 1.7 million of loss from the extinguishment of debt , and $ 1.1 million in amortization of debt discount and issuance costs . 77 for the year ended december 31 , 2018 , net cash used in operating activities was $ 40.3 million , which included a net loss of $ 62.0 million .
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 Suspicious Activity Report : the ongoing covid-19 surge , coupled alongside vaccine rollout logistics , likely indicate that our country and national healthcare system will be under some amount of continued strain over the coming months . that said , we continue to be encouraged as we witness meaningful evidence that the healthcare provider ecosystem is significantly better equipped and prepared to respond to the ongoing pandemic , including through its treatment efficacy , supply chain logistics , capacity planning , and broader operational optimization . lastly , we see additional reasons for optimism over the near-to-medium term , as we begin to witness early signs of progress on vaccine rollout logistics . we are fortunate to have a highly recurring revenue model in which greater than 90 % of our revenue is recurring in nature . as such , we expect that the near-term impact of covid-19 on our total revenue will be relatively muted , as evidenced by our revenue performance for the year ended december 31 , 2020. additionally , we benefit from a high level of technology revenue predictability , especially our dos subscription customers that typically have built-in , contractual technology revenue escalators . we also have developed a number of technology and services solutions designed specifically to support healthcare providers during the covid-19 pandemic . importantly , since the onset of the covid-19 pandemic , our customers ' overall usage of our data platform has increased meaningfully . additionally , we have seen usage of our covid-19-specific products shift from those focused on covid-19 preparedness to those focused on financial recovery and planning analytics in areas such as elective procedures , ambulatory care , and revenue cycle . given these factors , we have seen minimal impact on our technology dollar-based retention as a result of covid-19 and would anticipate similar dynamics moving forward . regarding our professional services , we continue to see high levels of engagement of our team member base , who remain engaged on both covid-19-recovery work as well as focusing on more general clinical , financial , and operational improvement work . that said , the financial strain imposed by covid-19 on a number of our customers has led to a meaningfully lower professional services dollar-based retention than we have achieved historically . the primary drivers for the decrease in our adjusted professional services gross margin from 35 % for the year ended december 31 , 2019 to 25 % for the year ended december 31 , 2020 include the lower professional services dollar-based retention mentioned above , temporary professional services discounts provided to support our customers through the near-term financial strain they have experienced related to covid-19 , as well as some shift in the mix of professional services delivered . we added nine net new dos subscription customers during the year ended december 31 , 2020. in the first half of 2020 , given the significant impact of covid-19 on our healthcare provider end market , the number of first half new customer additions was meaningfully lower than we originally anticipated entering the year . as we entered the second half of 2020 , we were pleased to see healthcare organizations adjusting well to the `` new normal `` operating environment , with covid-19 highlighting the need for a more robust , commercial-grade data and analytics solution . likewise , given the financial strain imposed by the pandemic , prospective customers have shown an increased focus on revenue and cost optimization analytics , from which we believe we are well positioned to benefit . on the other hand , the covid-19 pandemic continued to create some near-term financial uncertainty , making some health systems more cautious in their near-term purchasing decisions . given these operating dynamics , in the second half of 2020 we experienced similar overall pipeline conversion rates to the second half of 2019. any negative impact to 2020 total revenue caused by the covid-19 pandemic has also resulted in a negative impact to our 2020 adjusted ebitda . we have and continue to plan to partially offset any negative total revenue impact through cost containment efforts , resulting in less of a negative adjusted ebitda impact compared to the negative total revenue impact . importantly , in our response to the covid-19 pandemic , we remain centrally committed to our team members , ensuring they stay at the center of the health catalyst flywheel . as such , any cost containment efforts implemented will have a bias towards non-headcount related items . over the long run , as we get through the covid-19 pandemic and healthcare organizations ' operations begin to normalize , we continue to be optimistic that the pandemic will serve as an overall tailwind in the industry 's adoption of data and analytics . at the health system level , we are seeing meaningful evidence that covid-19 is highlighting the need for a commercial-grade data and analytics solution to replace patchwork homegrown systems . 62 our business model we offer our solution to a variety of healthcare organizations , primarily in the united states , including academic medical centers , integrated delivery networks , community hospitals , large physician practices , acos , health information exchanges , health insurers , and other risk-bearing entities . we categorize our customer count into two primary categories : dos subscription customers and other customers . dos subscription customers are defined as customers who access our dos platform via a technology subscription contract . other customers generally include dos non-subscription customers and other customers from historical acquisitions . as of december 31 , 2020 , 2019 , and 2018 , we had 74 , 65 , and 50 dos subscription customers with active subscriptions , respectively . story_separator_special_tag components of our results of operations revenue we derive our revenue from sales of technology and professional services . for the years ended december 31 , 2020 , 2019 , and 2018 , technology revenue represented 58 % , 54 % , and 51 % of total revenue , respectively , and professional services revenue represented 42 % , 46 % , and 49 % of total revenue , respectively . technology revenue . technology revenue primarily consists of subscription fees charged to customers for access to use our data platform and analytics applications . we provide customers access to our technology through either an all-access or limited-access , modular subscription . most of our subscription contracts are cloud-based and have up to a three-year term , of which the vast majority are terminable after one year upon 90 days ' notice . dos subscription customers that access our technology through an all-access or limited access , modular subscription generally have agreements with built-in annual escalators for technology access fees . also included in technology revenue is the maintenance and support we provide , which generally includes updates and support services . professional services revenue . professional services revenue primarily includes analytics services , domain expertise services , outsourcing services , and implementation services . professional services arrangements typically include a fee for making full-time equivalent ( fte ) services available to our customers on a monthly basis . fte services generally consist of a blend of analytic engineers , analysts , and data scientists based on the domain expertise needed to best serve our customers . 67 deferred revenue deferred revenue consists of customer billings in advance of revenue being recognized from our technology and professional services arrangements . we primarily invoice our customers for technology arrangements annually or quarterly in advance . amounts anticipated to be recognized within one year of the balance sheet date are recorded as deferred revenue and the remaining portion is recorded as deferred revenue , net of current portion on the consolidated balance sheets . cost of revenue , excluding depreciation and amortization cost of technology revenue . cost of technology revenue primarily consists of costs associated with hosting and supporting our technology , including third-party cloud computing and hosting costs , contractor costs , and salary and related personnel costs for our cloud services and support teams . although we expect cost of technology revenue to increase in absolute dollars as we transition customers to third-party hosted data centers with microsoft azure and increase headcount to accommodate growth , we anticipate cost of technology revenue as a percentage of technology revenue will generally decrease over the long term . we expect cost of technology revenue as a percentage of technology revenue to fluctuate and potentially increase in the near term , primarily due to additional costs associated with transitioning customers from on-premise and our managed data centers to microsoft azure . cost of professional services revenue . cost of professional services revenue consists primarily of costs related to delivering our team 's expertise in analytics , strategic advisory , improvement , and implementation services . these costs primarily include salary and related personnel costs , travel-related costs , and outside contractor costs . we expect cost of professional services revenue to increase in absolute dollars as we increase headcount to accommodate growth . operating expense sales and marketing . sales and marketing expenses primarily include salary and related personnel costs for our sales , marketing , and account management teams , lead generation , marketing events , including our healthcare analytics summit ( has ) , marketing programs , and outside contractor costs associated with the sale and marketing of our offerings . we plan to continue to invest in sales and marketing to grow our customer base , expand in new markets , and increase our brand awareness . the trend and timing of sales and marketing expenses will depend in part on the timing of our expansion into new markets and marketing campaigns . we expect that sales and marketing expenses will increase in absolute dollars in future periods , but decrease as a percentage of our revenue over the long term . our sales and marketing expenses may fluctuate as a percentage of our revenue from period to period due to the timing and extent of these expenses . research and development . research and development expenses primarily include salary and related personnel costs for our data platform and analytics applications teams , subscriptions , and outside contractor costs associated with the development of products . we have developed an open , flexible , and scalable data platform . we plan to continue to invest in research and development to develop new solutions and enhance our applications library . we expect that research and development expenses will increase in absolute dollars in future periods , but decrease as a percentage of our revenue over the long term . our research and development expenses may fluctuate as a percentage of our revenue from period to period due to the timing and extent of these expenses . general and administrative . general and administrative expenses primarily include salary and related personnel costs for our legal , finance , people operations , it , and other administrative teams , including certain executives . general and administrative expenses also include facilities , subscriptions , corporate insurance , outside legal , accounting , and directors ' fees . due to the closing of our ipo on july 29 , 2019 , we incurred and expect to continue to incur additional costs as a result of operating as a public company , including costs related to compliance and reporting obligations of public companies , and increased costs for insurance , investor relations , and corporate governance . as a result , we expect our general and administrative expenses to increase in absolute dollars for the foreseeable future , but decrease as a percentage of our

