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 , if earlier , 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: .

2017
2016
2015
Balance at beginning of year
$44.0
$46.7
$38.9
Additions charged to expense
30.6
20.4
22.7
Accounts written-off
(35.7)
(23.1)
(14.9)
Balance at end of year
$38.9
$44.0
$46.7

restricted cash and marketable securities as of december 31 , 2017 , we had $ 141.1 million of restricted cash and marketable securities of which $ 71.4 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 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 .
property and equipment we record property and equipment at cost .
expenditures for major additions and improvements to facilities are capitalized , while maintenance and repairs are charged to expense as incurred .
when property is retired or .

Question: Analyse this data from a financial earnings document. as of december 31 , 2017 what was the ratio of restricted cash and marketable securities for the supports our insurance programs for workers 2019 compensation , commercial general liability , and commercial auto liability to the total restricted cash and marketable securities
Choices:
1.97619
10074.54
0.50602
0.31184
0.63785
Correct choice index: 2