December 31,
(in thousands of $)
2018
2017
Change
% Change
Total operating revenues
127,625
—
127,625
100%
Vessel operating expenses
(26,317)
(2)
(26,315)
1,315,750%
Voyage expenses
(1,363)
(121)
(1,242)
1,026%
Administrative expenses
175
(1,736)
1,911
(110)%
Project development expenses
(16,526)
(2,506)
(14,020)
559%
Depreciation and amortization
(28,193)
—
(28,193)
100%
Other operating gains
2,749
15,100
(12,351)
(82)%
Operating income
58,150
10,735
47,415
442%
Equity in net losses of affiliates
(2,047)
(8,153)
6,106
(75)%

text: FLNG segment
text: Total operating revenues: On May 31, 2018, the Hilli was accepted by the Customer and, accordingly, commenced operations. As a result, she generated $127.6 million total operating revenues in relation to her liquefaction services for the year ended December 31, 2018.
text: Vessel operating expenses: This represents the vessel operating expenses incurred by the Hilli since she commenced operations.
text: Project development expenses: This relates to non-capitalized project-related expenses comprising of legal, professional and consultancy costs. The increase for the twelve months ended December 31, 2018 was primarily as a result of increased engineering consultation fees and front-end engineering and design costs in relation to the Gimi GTA project.
text: Depreciation: Subsequent to the Customer's acceptance of the Hilli, we determined her to be operational and, therefore, depreciation commenced during the second quarter of 2018.
text: Other operating gains: Includes the realized and unrealized gain on the oil derivative instrument. In 2018, we recognized a realized gain of $26.7 million, and an unrealized fair value loss of $10.0 million, relating to the LTA oil derivative instrument as a result of the increased price of Brent Crude during the year. The derivative asset was recognized upon the LTA becoming effective in December 2017. In 2017, we recognized an unrealized fair value gain of $15.1 million.
text: For the year ended December 31, 2018, this is partially offset by a $1.3 million write off of capitalized conversion costs in relation to the Gandria. In addition, subsequent to the decision to wind down OneLNG, we wrote off $12.7 million of the trading balance with OneLNG as we deem it to be no longer recoverable.
text: Equity in net losses of affiliates: Pursuant to the formation of OneLNG in July 2016, we equity account for our share of net losses in OneLNG. Given the difficulties in finalizing an attractive debt financing package along with other capital and resource priorities, in April 2018, Golar and Schlumberger decided to wind down OneLNG and work on FLNG projects as required on a case-by-case basis. As a result, activity levels have been substantially reduced for the year ended December 31, 2018 and the carrying value of the investment was written down to $nil.

Questions:
question: Why did the activity levels decrease in 2018?
answer: Golar and Schlumberger decided to wind down OneLNG and work on FLNG projects as required on a case-by-case basis
question: What was the realized gain on the oil derivative instrument?
answer: $26.7 million
question: What are the different components of expenses?
answer: Vessel operating expenses
Voyage expenses
Administrative expenses
Project development expenses
Depreciation and amortization
question: In which year was the project development expenses higher?
answer: 2018
derivation: (16,526) > (2,506)
question: What was the change in total operating revenues between 2017 and 2018?
answer: 127625
derivation: 127,625 - 0 
scale: thousand
question: What was the percentage change in operating income between 2017 and 2018?
answer: 441.69
derivation: (58,150 - 10,735)/10,735 
scale: percent