pre_text: GasLog Ltd. and its Subsidiaries
  Notes to the consolidated financial statements (Continued)
  For the years ended December 31, 2017, 2018 and 2019
  (All amounts expressed in thousands of U.S. Dollars, except share and per share data) 14. Other Payables and Accruals An analysis of other payables and accruals is as follows: The unearned revenue represents charter hires received in advance in December 2019 relating to the hire period of January 2020 for 22 vessels (December 2018: 17 vessels).
table: As of December 31,
table: 2018 2019
table: Unearned revenue 38,680 48,183
table: Accrued off-hire 7,376 6,968
table: Accrued purchases 18,578 9,759
table: Accrued interest 38,107 36,746
table: Other accruals 24,709 34,586
table: Total 127,450 136,242
question: Analyse this data from a financial earnings document. What was the change in accrued purchases from 2018 to 2019?