pre_text: 15 Financial risk management (continued) (b) Credit risk Credit risk arises from cash and cash equivalents, and trade and other receivables. (i) Cash and cash equivalents and security deposits Deposits are placed with Australian banks or independently rated parties with a minimum rating of ‘BBB+’. To reduce exposure deposits are placed with a variety of financial institutions. The credit quality of financial assets can be assessed by reference to external credit ratings (if available) or to historical information about counterparty default rates: In determining the credit quality of these financial assets, NEXTDC has used the long-term rating from Standard & Poor’s as of July 2019.
table: 30 June 2019 30 June 2018
table: $'000 $'000
table: CASH AT BANK
table: AA rated 398,999 417,982
table: SECURITY DEPOSITS
table: AA rated 8,822 4,151
question: Analyse this data from a financial earnings document. What was the average difference between cash at bank and security deposits for both years?