(9) Trade receivables

All trade receivables – totaling €1,070 million (2012: €1,117 million) – are due within one year. Of the trade receivables, €3 million (2012: €4 million) pertained to investments accounted for using the equity method and €1,067 million (2012: €1,113 million) to other customers.

Trade receivables are stated after write-downs of €18 million (2012: €13 million) on gross receivables of €19 million (2012: €21 million).

The changes in write-downs of trade receivables were as follows:

Write-Downs of Trade Receivables
 
€ million 2012 2013
     
Balance at beginning of year (13) (13)
Additions charged as expenses (4) (9)
Reversals/utilization 4 3
Exchange differences 0 1
Balance at end of year (13) (18)
 

The maturity structure of past-due trade receivables was as follows:

Maturity Structure of Past-Due Trade Receivables
 
€ million Dec. 31, 2012 Dec. 31, 2013
     
Carrying amount 1,117 1,070
of which neither impaired nor past due 973 939
of which unimpaired but past due by    
up to 30 days 112 106
between 31 and 60 days 10 12
between 61 and 90 days 3 7
more than 90 days 11 5
 

With regard to trade receivables that were neither impaired nor past due, there were no indications as of the closing date that the respective debtors would not meet their payment obligations.