in the normal course of business , we experience contract cancellations , which are reflected as cancellations when the client provides us with written or electronic correspondence that the work should cease . during the years ended december 31 , 2019 and 2018 , we had $ 360.4 million and $ 378.8 million , respectively , of cancellations for which we received correspondence from the client . the number of cancellations can vary significantly from year to year . the value of the cancellation is the remaining amount of unrecognized service revenue , less the estimated effort to transition the work back to the client . our backlog consists of anticipated service revenue from new business awards that either have not started or are in process but have not been completed . backlog varies from period to period depending upon new business awards and contract modifications , cancellations , and the amount of service revenue recognized under existing contracts . our backlog at december 31 , 2019 and 2018 was $ 4.7 billion and $ 4.2 billion , respectively . 37 industry trends isr estimated in its 2019 market report that the size of the worldwide cro market was approximately $ 39 billion in 2018 and will grow at a 7.5 % cagr to $ 56 billion in 2023. this growth will be driven by an increase in the amount of research and development expenditures and higher levels of clinical development outsourcing by biopharmaceutical companies . sources of revenue total revenue is comprised of revenue from the provision of our services , and revenue from reimbursable expenses and reimbursable investigator grants , that are incurred while providing our services . we do not have any material product revenue . on january 1 , 2018 , we adopted asc 606 “ revenue from contracts with customers , ” or asc 606 , using the modified retrospective method for all contracts that were not completed as of january 1 , 2018. thus , in this part ii item 7 and elsewhere in this report , we report 2019 and 2018 fiscal year revenue under the modified retrospective method of asc 606 , and continue to report comparative prior period information for the 2017 fiscal year under the accounting standards in effect for that period . see note 3 to our audited consolidated financial statements found elsewhere in this annual report on form 10-k for additional details regarding our sources of revenue . costs and expenses our costs and expenses are comprised primarily of our direct costs , selling , general and administrative costs , depreciation and amortization and income taxes . in addition , we monitor and measure costs as a percentage of revenue , excluding reimbursement revenue from reimbursable expenses , rather than total revenue , as we believe this is a more meaningful comparison and better reflects the operations of our business . direct costs ( exclusive of depreciation and amortization ) for our clinical research segment , direct costs consist primarily of labor‑related charges . they include elements such as salaries , benefits and incentive compensation for our employees . in addition , we utilize staffing agencies to procure primarily part time individuals to perform work on our contracts . labor-related charges as a percentage of the clinical research segment 's total direct costs were 96.4 % and 96.0 % for the years ended december 31 , 2019 and 2018 , respectively . the cost of labor procured through staffing agencies is included in these percentages and represents 3.1 % and 4.5 % of the clinical research segment 's total direct costs for the years ended december 31 , 2019 and 2018 , respectively . our remaining direct costs are items such as travel , meals , postage and freight , patient costs , medical waste and supplies . the total of all these items as a percentage of the clinical research segment 's total direct costs were 3.6 % and 4.0 % for the years ended december 31 , 2019 and 2018 , respectively . for our data solutions segment , direct costs consist primarily of data costs . data costs as a percentage of the data solutions segment 's total direct costs were 73.3 % and 73.0 % for the years ended december 31 , 2019 and 2018 , respectively . labor-related charges , such as salaries , benefits and incentive compensation for our employees , were 20.2 % and 20.3 % of the data solutions segment 's total direct costs for the years ended december 31 , 2019 and 2018 , respectively . our remaining direct costs are items such as travel , meals , and supplies and were 6.5 % and 6.7 % of the data solutions segment 's total direct costs for the years ended december 31 , 2019 and 2018 , respectively . historically , direct costs have increased with an increase in revenue . the future relationship between direct costs and revenue may vary from historical relationships . direct costs as a percentage of revenue were 50.2 % and 52.2 % , during the years ended december 31 , 2019 and 2018 , respectively . several factors will cause direct costs to decrease as a percentage of revenue . deployment of our billable staff in an optimally efficient manner has the greatest impact on our ratio of direct cost to revenue . the most effective deployment of our staff is when they are fully engaged in billable work and are accomplishing contract related activities at a rate that meets or exceeds budgeted targets . we also seek to optimize our efficiency by performing work using the employee with the lowest cost . story_separator_special_tag 43 liquidity and capital resources we assess our liquidity in terms of our ability to generate cash to fund our operating , investing and financing activities . our principal source of liquidity is operating cash flows . as of december 31 , 2019 , we had approximately $ 236.2 million of cash and cash equivalents of which $ 86.9 million was held by our foreign subsidiaries . our expected primary cash needs on both a short and long‑term basis are for capital expenditures , expansion of services , geographic expansion , debt repayments , and other general corporate purposes . we have historically funded our operations and growth , including acquisitions , with cash flow from operations , borrowings , and issuances of equity securities . we expect to continue expanding our operations through internal growth and strategic acquisitions and investments . we expect these activities will be funded from existing cash , cash flow from operations and , if necessary or appropriate , borrowings under our existing or future credit facilities . our sources of liquidity could be affected by our dependence on a small number of industries and clients , compliance with regulations , international risks , and personal injury , environmental or other material litigation claims . story_separator_special_tag style= `` font-family : inherit ; font-size:10pt ; `` > the foregoing mandatory prepayments will be applied first to accrued interest and fees and second , to the scheduled installments of principal of the senior secured credit facility in direct order of maturity . we may voluntarily repay outstanding loans under the senior secured credit facility at any time without premium or penalty , subject to reimbursements of the lenders ' redeployment costs actually incurred in the case of a prepayment of libor borrowings other than on the last day of the relevant interest period . amortization and final maturity the first lien term loan is a floating rate term loan with scheduled , fixed quarterly principal payments of $ 6.3 million to be made quarterly until october 28 , 2024. we have the option of one- , two- , three- or six-month borrowing terms under the revolver . principal amounts outstanding under the revolver are due and payable in full at maturity , on or about october 28 , 2024. guarantee and security all obligations of the borrower under the senior secured credit facility are unconditionally guaranteed by us and all our material , wholly‑owned u.s. restricted subsidiaries with customary exceptions , including where providing such guarantees is not permitted by law , regulation or contract or would result in material adverse tax consequences . all obligations of the borrower under the senior secured credit facility , and the guarantees of such obligations , are secured , subject to permitted liens and other exceptions , by substantially all of the assets of the borrower and each guarantor , including but not limited to : ( i ) a perfected pledge of all of the capital stock issued by the borrower and each guarantor and ( ii ) perfected security interests in substantially all other tangible and intangible assets of the borrower and the guarantors ( subject to certain exceptions and exclusions ) . certain covenants and events of default the senior secured credit facility contains a number of covenants that , among other things , restrict , subject to certain exceptions , our ability to : create any liens ; make investments and acquisitions ; incur or guarantee additional indebtedness ; enter into mergers or consolidations and other fundamental changes ; conduct sales and other dispositions of property or assets ; enter into sale-leaseback transactions or hedge agreements ; prepay subordinated debt ; pay dividends or make other payments in respect of capital stock ; change the line of business ; enter into transactions with affiliates ; enter into burdensome agreements with negative pledge clauses and clauses restriction ; and 46 subsidiary distributions . our senior secured credit facility contains customary events of default ( subject to exceptions , thresholds and grace periods ) , including , without limitation : ( i ) nonpayment of principal or interest ; ( ii ) failure to perform or observe covenants ; ( iii ) inaccuracy or breaches of representations and warranties ; ( iv ) cross‑defaults with certain other indebtedness ; ( v ) certain bankruptcy related events ; ( vi ) impairment of certain security interests in collateral , guarantees or invalidity or unenforceability of certain senior secured credit facility documents ; ( vii ) monetary judgment defaults ; ( viii ) certain erisa matters ; and ( ix ) certain change of control events . the senior secured credit facility requires us to maintain a consolidated total debt to consolidated ebitda ratio of 4.25 to 1.0 and consolidated ebitda to fixed charges no less than 3.0 to 1.0 for any four consecutive fiscal quarters for which financial statements have been provided to the administrative agent as required by the senior secured credit agreement . following a qualified material acquisition , the senior secured credit facility allows us to increase its consolidated total debt to consolidated ebitda ratio to 5.25 to 1.00 ; provided that ( i ) such ratio in respect of each quarter shall be reduced by 0.25 to 1.00 , ( ii ) in no event shall such ratio be lower than 4.25 to 1.00 and ( iii ) such an increase pursuant to this shall be permitted no more than once during any period of 24 consecutive months . the senior secured credit facility also contains certain customary affirmative covenants and events of default , including a change of control . accounts receivable financing agreement we entered into an accounts receivable financing agreement with pnc bank , national association , as administrative agent and lender on march 22 , 2016. on may 31 , 2018 , we amended our accounts receivable financing agreement . the amendment increased the agreement 's borrowing capacity , decreased the

cash collections cash collections from accounts receivable were $ 3,087.3 million during the year ended december 31 , 2019 , including $ 325.3 million of funds received from customers to pay independent physician investigators , or investigators , as compared to $ 2,894.4 million during the year ended december 31 , 2018 , including $ 293.6 million of funds received from customers to pay investigators . the increase in cash collections is related to our increase in revenue , driven by an increase in new business awards and backlog . discussion of cash flows cash flow from operating activities during the year ended december 31 , 2019 , net cash provided by operations was $ 253.6 million , compared to $ 329.8 million in 2018 . cash provided by operating activities decreased from the prior year primarily due to an increase in cash outflows associated with acquisition related earn-out payments as well as an increase in cash outflows from working capital . the changes in working capital were driven by changes in our accounts receivable , unbilled services and advanced billings accounts , as a result of a slight increase in our days sales outstanding compared to the prior year . cash flow from investing activities net cash used in investing activities was $ 73.2 million during the year ended december 31 , 2019 , compared to $ 55.5 million in 2018 . the increase in cash outflows is attributable to spending on capital expenditures , as we made increased investments in our information technology infrastructure and the build-out of new office space added to support our growing business . cash flow from financing activities net cash used in financing activities was $ 90.7 million during the year ended december 31 , 2019 compared to $ 319.5 million for the same period of 2018 . during the year ended december 31 , 2019 , our long-term debt balance , including borrowings under our revolving line of credit , increased by $ 172.3 million compared to a $ 265.9 million decrease due to payments on our debt during the year ended december 31 , 2018 .


 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 collections cash collections from accounts receivable were $ 3,087.3 million during the year ended december 31 , 2019 , including $ 325.3 million of funds received from customers to pay independent physician investigators , or investigators , as compared to $ 2,894.4 million during the year ended december 31 , 2018 , including $ 293.6 million of funds received from customers to pay investigators . the increase in cash collections is related to our increase in revenue , driven by an increase in new business awards and backlog . discussion of cash flows cash flow from operating activities during the year ended december 31 , 2019 , net cash provided by operations was $ 253.6 million , compared to $ 329.8 million in 2018 . cash provided by operating activities decreased from the prior year primarily due to an increase in cash outflows associated with acquisition related earn-out payments as well as an increase in cash outflows from working capital . the changes in working capital were driven by changes in our accounts receivable , unbilled services and advanced billings accounts , as a result of a slight increase in our days sales outstanding compared to the prior year . cash flow from investing activities net cash used in investing activities was $ 73.2 million during the year ended december 31 , 2019 , compared to $ 55.5 million in 2018 . the increase in cash outflows is attributable to spending on capital expenditures , as we made increased investments in our information technology infrastructure and the build-out of new office space added to support our growing business . cash flow from financing activities net cash used in financing activities was $ 90.7 million during the year ended december 31 , 2019 compared to $ 319.5 million for the same period of 2018 . during the year ended december 31 , 2019 , our long-term debt balance , including borrowings under our revolving line of credit , increased by $ 172.3 million compared to a $ 265.9 million decrease due to payments on our debt during the year ended december 31 , 2018 .
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 Suspicious Activity Report : in the normal course of business , we experience contract cancellations , which are reflected as cancellations when the client provides us with written or electronic correspondence that the work should cease . during the years ended december 31 , 2019 and 2018 , we had $ 360.4 million and $ 378.8 million , respectively , of cancellations for which we received correspondence from the client . the number of cancellations can vary significantly from year to year . the value of the cancellation is the remaining amount of unrecognized service revenue , less the estimated effort to transition the work back to the client . our backlog consists of anticipated service revenue from new business awards that either have not started or are in process but have not been completed . backlog varies from period to period depending upon new business awards and contract modifications , cancellations , and the amount of service revenue recognized under existing contracts . our backlog at december 31 , 2019 and 2018 was $ 4.7 billion and $ 4.2 billion , respectively . 37 industry trends isr estimated in its 2019 market report that the size of the worldwide cro market was approximately $ 39 billion in 2018 and will grow at a 7.5 % cagr to $ 56 billion in 2023. this growth will be driven by an increase in the amount of research and development expenditures and higher levels of clinical development outsourcing by biopharmaceutical companies . sources of revenue total revenue is comprised of revenue from the provision of our services , and revenue from reimbursable expenses and reimbursable investigator grants , that are incurred while providing our services . we do not have any material product revenue . on january 1 , 2018 , we adopted asc 606 “ revenue from contracts with customers , ” or asc 606 , using the modified retrospective method for all contracts that were not completed as of january 1 , 2018. thus , in this part ii item 7 and elsewhere in this report , we report 2019 and 2018 fiscal year revenue under the modified retrospective method of asc 606 , and continue to report comparative prior period information for the 2017 fiscal year under the accounting standards in effect for that period . see note 3 to our audited consolidated financial statements found elsewhere in this annual report on form 10-k for additional details regarding our sources of revenue . costs and expenses our costs and expenses are comprised primarily of our direct costs , selling , general and administrative costs , depreciation and amortization and income taxes . in addition , we monitor and measure costs as a percentage of revenue , excluding reimbursement revenue from reimbursable expenses , rather than total revenue , as we believe this is a more meaningful comparison and better reflects the operations of our business . direct costs ( exclusive of depreciation and amortization ) for our clinical research segment , direct costs consist primarily of labor‑related charges . they include elements such as salaries , benefits and incentive compensation for our employees . in addition , we utilize staffing agencies to procure primarily part time individuals to perform work on our contracts . labor-related charges as a percentage of the clinical research segment 's total direct costs were 96.4 % and 96.0 % for the years ended december 31 , 2019 and 2018 , respectively . the cost of labor procured through staffing agencies is included in these percentages and represents 3.1 % and 4.5 % of the clinical research segment 's total direct costs for the years ended december 31 , 2019 and 2018 , respectively . our remaining direct costs are items such as travel , meals , postage and freight , patient costs , medical waste and supplies . the total of all these items as a percentage of the clinical research segment 's total direct costs were 3.6 % and 4.0 % for the years ended december 31 , 2019 and 2018 , respectively . for our data solutions segment , direct costs consist primarily of data costs . data costs as a percentage of the data solutions segment 's total direct costs were 73.3 % and 73.0 % for the years ended december 31 , 2019 and 2018 , respectively . labor-related charges , such as salaries , benefits and incentive compensation for our employees , were 20.2 % and 20.3 % of the data solutions segment 's total direct costs for the years ended december 31 , 2019 and 2018 , respectively . our remaining direct costs are items such as travel , meals , and supplies and were 6.5 % and 6.7 % of the data solutions segment 's total direct costs for the years ended december 31 , 2019 and 2018 , respectively . historically , direct costs have increased with an increase in revenue . the future relationship between direct costs and revenue may vary from historical relationships . direct costs as a percentage of revenue were 50.2 % and 52.2 % , during the years ended december 31 , 2019 and 2018 , respectively . several factors will cause direct costs to decrease as a percentage of revenue . deployment of our billable staff in an optimally efficient manner has the greatest impact on our ratio of direct cost to revenue . the most effective deployment of our staff is when they are fully engaged in billable work and are accomplishing contract related activities at a rate that meets or exceeds budgeted targets . we also seek to optimize our efficiency by performing work using the employee with the lowest cost . story_separator_special_tag 43 liquidity and capital resources we assess our liquidity in terms of our ability to generate cash to fund our operating , investing and financing activities . our principal source of liquidity is operating cash flows . as of december 31 , 2019 , we had approximately $ 236.2 million of cash and cash equivalents of which $ 86.9 million was held by our foreign subsidiaries . our expected primary cash needs on both a short and long‑term basis are for capital expenditures , expansion of services , geographic expansion , debt repayments , and other general corporate purposes . we have historically funded our operations and growth , including acquisitions , with cash flow from operations , borrowings , and issuances of equity securities . we expect to continue expanding our operations through internal growth and strategic acquisitions and investments . we expect these activities will be funded from existing cash , cash flow from operations and , if necessary or appropriate , borrowings under our existing or future credit facilities . our sources of liquidity could be affected by our dependence on a small number of industries and clients , compliance with regulations , international risks , and personal injury , environmental or other material litigation claims . story_separator_special_tag style= `` font-family : inherit ; font-size:10pt ; `` > the foregoing mandatory prepayments will be applied first to accrued interest and fees and second , to the scheduled installments of principal of the senior secured credit facility in direct order of maturity . we may voluntarily repay outstanding loans under the senior secured credit facility at any time without premium or penalty , subject to reimbursements of the lenders ' redeployment costs actually incurred in the case of a prepayment of libor borrowings other than on the last day of the relevant interest period . amortization and final maturity the first lien term loan is a floating rate term loan with scheduled , fixed quarterly principal payments of $ 6.3 million to be made quarterly until october 28 , 2024. we have the option of one- , two- , three- or six-month borrowing terms under the revolver . principal amounts outstanding under the revolver are due and payable in full at maturity , on or about october 28 , 2024. guarantee and security all obligations of the borrower under the senior secured credit facility are unconditionally guaranteed by us and all our material , wholly‑owned u.s. restricted subsidiaries with customary exceptions , including where providing such guarantees is not permitted by law , regulation or contract or would result in material adverse tax consequences . all obligations of the borrower under the senior secured credit facility , and the guarantees of such obligations , are secured , subject to permitted liens and other exceptions , by substantially all of the assets of the borrower and each guarantor , including but not limited to : ( i ) a perfected pledge of all of the capital stock issued by the borrower and each guarantor and ( ii ) perfected security interests in substantially all other tangible and intangible assets of the borrower and the guarantors ( subject to certain exceptions and exclusions ) . certain covenants and events of default the senior secured credit facility contains a number of covenants that , among other things , restrict , subject to certain exceptions , our ability to : create any liens ; make investments and acquisitions ; incur or guarantee additional indebtedness ; enter into mergers or consolidations and other fundamental changes ; conduct sales and other dispositions of property or assets ; enter into sale-leaseback transactions or hedge agreements ; prepay subordinated debt ; pay dividends or make other payments in respect of capital stock ; change the line of business ; enter into transactions with affiliates ; enter into burdensome agreements with negative pledge clauses and clauses restriction ; and 46 subsidiary distributions . our senior secured credit facility contains customary events of default ( subject to exceptions , thresholds and grace periods ) , including , without limitation : ( i ) nonpayment of principal or interest ; ( ii ) failure to perform or observe covenants ; ( iii ) inaccuracy or breaches of representations and warranties ; ( iv ) cross‑defaults with certain other indebtedness ; ( v ) certain bankruptcy related events ; ( vi ) impairment of certain security interests in collateral , guarantees or invalidity or unenforceability of certain senior secured credit facility documents ; ( vii ) monetary judgment defaults ; ( viii ) certain erisa matters ; and ( ix ) certain change of control events . the senior secured credit facility requires us to maintain a consolidated total debt to consolidated ebitda ratio of 4.25 to 1.0 and consolidated ebitda to fixed charges no less than 3.0 to 1.0 for any four consecutive fiscal quarters for which financial statements have been provided to the administrative agent as required by the senior secured credit agreement . following a qualified material acquisition , the senior secured credit facility allows us to increase its consolidated total debt to consolidated ebitda ratio to 5.25 to 1.00 ; provided that ( i ) such ratio in respect of each quarter shall be reduced by 0.25 to 1.00 , ( ii ) in no event shall such ratio be lower than 4.25 to 1.00 and ( iii ) such an increase pursuant to this shall be permitted no more than once during any period of 24 consecutive months . the senior secured credit facility also contains certain customary affirmative covenants and events of default , including a change of control . accounts receivable financing agreement we entered into an accounts receivable financing agreement with pnc bank , national association , as administrative agent and lender on march 22 , 2016. on may 31 , 2018 , we amended our accounts receivable financing agreement . the amendment increased the agreement 's borrowing capacity , decreased the

