Table:
|  | As of  December 31, |  |
| --- | --- | --- |
|  | 2018 | 2019 |
| Progress shipyard installments | 152,075 | 197,637 |
| Onsite supervision costs | 5,766 | 3,879 |
| Critical spare parts, equipment and other vessel delivery expenses | 1,434 | 1,807 |
| Total | 159,275 | 203,323 |
Paragraphs:
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)
Vessels under construction represent scheduled advance payments to the shipyards as well as certain capitalized expenditures. As of December 31, 2019, the Group has paid to the shipyard $197,637 for the vessels that are under construction and expects to pay the remaining installments as they come due upon each vessel’s keel laying, launching and delivery (Note 23(a)).
The vessels under construction costs as of December 31, 2018 and 2019 are comprised of:
Question:
What was the change in onsite supervision costs  from 2018 to 2019 ?
Answer: 3879 - 5766  = -1887