Year Ended December 31, 2017 Compared to Year Ended December 31, 2018
During the year ended December 31, 2018, we had an average of 26.0 ships operating in our owned and bareboat fleet (including ships owned by the Partnership), having 9,030 operating days and an average of 25.5 ships operating under our technical management (including 25.0 of our owned and bareboat ships). During the year ended December 31, 2017, we had an average of 23.0 ships operating in our owned and bareboat fleet having 8,317 operating days and an average of 23.4 ships operating under our technical management (including 22.0 of our owned ships).
Revenues: Revenues increased by 17.7%, or $93.1 million, from $525.2 million during the year ended December 31, 2017 to $618.3 million during the year ended December 31, 2018. The increase in revenues is mainly attributable to an increase of $64.2 million in revenues from our vessels operating in the spot market due to the significant increase in LNG shipping spot rates during the year. There was also an increase in revenues of $63.7 million due to the deliveries of the GasLog Houston, the GasLog Hong Kong and the GasLog Genoa (which were delivered on January 8, 2018, March 20, 2018 and March 29, 2018, respectively). These deliveries resulted in an increase in operating days. These increases were partially offset by a decrease of $25.4 million due to the expiration of the initial time charters of the GasLog Shanghai, the GasLog Santiago and the GasLog Sydney. Following the expiration of their initial charters, the GasLog Shanghai has been trading in the spot market through the Cool Pool, the GasLog Santiago began a new, multi-year charter with Trafigura and the GasLog Sydney began a new 18-month charter with Cheniere. There was also a decrease of $8.4 million due to increased off-hire days for four scheduled dry-dockings in the year ended December 31, 2018 compared to only one scheduled dry-docking in the same period of 2017 and a decrease of $0.7 million due to increased off-hire days from the remaining vessels. The average daily hire rate increased from $63,006 for the year ended December 31, 2017 to $68,392 for the year ended December 31, 2018. Furthermore, there was a decrease of $0.3 million in revenues from technical management services mainly due to the decrease in the average number of the managed vessels owned by third parties.
Table:
 |  | Year ended December 31, | 
 | 2017 | 2018 | Change
Amounts are in thousands of U.S. Dollars |  |  | 
Revenues | $525,229 | $618,344 | $93,115
Net pool allocation | 7,254 | 17,818 | 10,564
Voyage expenses and commissions | (15,404) | (20,374) | (4,970)
Vessel operating and supervision costs | (122,486) | (128,084) | (5,598)
Depreciation | (137,187) | (153,193) | (16,006)
General and administrative expenses | (39,850) | (41,993) | (2,143)
Profit from operations | 217,556 | 292,518 | 74,962
Financial costs | (139,181) | (166,627) | (27,446)
Financial income | 2,650 | 4,784 | 2,134
Gain/(loss) on derivatives | 2,025 | (6,077) | (8,102)
Share of profit of associates | 1,159 | 1,800 | 641
Total other expenses, net | (133,347) | (166,120) | (32,773)
Profit for the year | 84,209 | 126,398 | 42,189
Non-controlling interests | 68,703 | 78,715 | 10,012
Profit attributable to owners of the Group | $15,506 | $47,683 | $32,177


Question: What was the reason for the increase in operating days?
Answer: Due to the deliveries of the GasLog Houston, the GasLog Hong Kong and the GasLog Genoa