republic services , inc . notes to consolidated financial statements 2014 ( continued ) high quality financial institutions . such balances may be in excess of fdic insured limits . to manage the related credit exposure , we continually monitor the credit worthiness of the financial institutions where we have deposits . concentrations of credit risk with respect to trade accounts receivable are limited due to the wide variety of customers and markets in which we provide services , as well as the dispersion of our operations across many geographic areas . we provide services to small-container , large-container , municipal and residential , and energy services customers in the united states and puerto rico . we perform ongoing credit evaluations of our customers , but generally do not require collateral to support customer receivables . we establish an allowance for doubtful accounts based on various factors including the credit risk of specific customers , age of receivables outstanding , historical trends , economic conditions and other information . accounts receivable , net accounts receivable represent receivables from customers for collection , transfer , recycling , disposal , energy services and other services . our receivables are recorded when billed or when the related revenue is earned and represent claims against third parties that will be settled in cash . the carrying value of our receivables , net of the allowance for doubtful accounts and customer credits , represents their estimated net realizable value . provisions for doubtful accounts are evaluated on a monthly basis and are recorded based on our historical collection experience , the age of the receivables , specific customer information and economic conditions . we also review outstanding balances on an account-specific basis . in general , reserves are provided for accounts receivable in excess of 90 days outstanding . past due receivable balances are written-off when our collection efforts have been unsuccessful in collecting amounts due . the following table reflects the activity in our allowance for doubtful accounts for the years ended december 31: .

Table:
 | 2018 | 2017 | 2016
balance at beginning of year | $ 38.9 | $ 44.0 | $ 46.7
additions charged to expense | 34.8 | 30.6 | 20.4
accounts written-off | ( 39.4 ) | ( 35.7 ) | ( 23.1 )
balance at end of year | $ 34.3 | $ 38.9 | $ 44.0
restricted cash and marketable securities as of december 31 , 2018 , we had $ 108.1 million of restricted cash and marketable securities of which $ 78.6 million supports our insurance programs for workers 2019 compensation , commercial general liability , and commercial auto liability .
additionally , we obtain funds through the issuance of tax-exempt bonds for the purpose of financing qualifying expenditures at our landfills , transfer stations , collection and recycling processing centers .
the funds are deposited directly into trust accounts by the bonding authorities at the time of issuance .
as the use of these funds is contractually restricted , and we do not have the ability to use these funds for general operating purposes , they are classified as restricted cash and marketable securities in our consolidated balance sheets .
in the normal course of business , we may be required to provide financial assurance to governmental agencies and a variety of other entities in connection with municipal residential collection contracts , closure or post- closure of landfills , environmental remediation , environmental permits , and business licenses and permits as a financial guarantee of our performance .
at several of our landfills , we satisfy financial assurance requirements by depositing cash into restricted trust funds or escrow accounts. .

Question: as of december 312018 what was the percent of restricted cash and marketable securities dedicated to the support our insurance programs
Answer: 72.7%
Calculation: divide(78.6, 108.1)