the goldman sachs group , inc . and subsidiaries management 2019s discussion and analysis investing & lending investing & lending includes our investing activities and the origination of loans , including our relationship lending activities , to provide financing to clients . these investments and loans are typically longer-term in nature . we make investments , some of which are consolidated , including through our merchant banking business and our special situations group , in debt securities and loans , public and private equity securities , infrastructure and real estate entities . some of these investments are made indirectly through funds that we manage . we also make unsecured and secured loans to retail clients through our digital platforms , marcus and goldman sachs private bank select ( gs select ) , respectively . the table below presents the operating results of our investing & lending segment. .
in millions for 2017 , 2016 , and 2015 , what was the minimum amount of equity securities?
operating environment . during 2017 , generally higher global equity prices and tighter credit spreads contributed to a favorable environment for our equity and debt investments . results also reflected net gains from company- specific events , including sales , and corporate performance . this environment contrasts with 2016 , where , in the first quarter of 2016 , market conditions were difficult and corporate performance , particularly in the energy sector , was impacted by a challenging macroeconomic environment . however , market conditions improved during the rest of 2016 as macroeconomic concerns moderated . if macroeconomic concerns negatively affect company-specific events or corporate performance , or if global equity markets decline or credit spreads widen , net revenues in investing & lending would likely be negatively impacted . 2017 versus 2016 . net revenues in investing & lending were $ 6.58 billion for 2017 , 61% ( 61 % ) higher than 2016 . net revenues in equity securities were $ 4.58 billion , including $ 3.82 billion of net gains from private equities and $ 762 million in net gains from public equities . net revenues in equity securities were 78% ( 78 % ) higher than 2016 , primarily reflecting a significant increase in net gains from private equities , which were positively impacted by company- specific events and corporate performance . in addition , net gains from public equities were significantly higher , as global equity prices increased during the year . of the $ 4.58 billion of net revenues in equity securities , approximately 60% ( 60 % ) was driven by net gains from company-specific events , such as sales , and public equities . net revenues in debt securities and loans were $ 2.00 billion , 33% ( 33 % ) higher than 2016 , reflecting significantly higher net interest income ( 2017 included approximately $ 1.80 billion of net interest income ) . net revenues in debt securities and loans for 2017 also included an impairment of approximately $ 130 million on a secured operating expenses were $ 2.80 billion for 2017 , 17% ( 17 % ) higher than 2016 , due to increased compensation and benefits expenses , reflecting higher net revenues , increased expenses related to consolidated investments , and increased expenses related to marcus . pre-tax earnings were $ 3.79 billion in 2017 compared with $ 1.69 billion in 2016 . 2016 versus 2015 . net revenues in investing & lending were $ 4.08 billion for 2016 , 25% ( 25 % ) lower than 2015 . net revenues in equity securities were $ 2.57 billion , including $ 2.17 billion of net gains from private equities and $ 402 million in net gains from public equities . net revenues in equity securities were 32% ( 32 % ) lower than 2015 , primarily reflecting a significant decrease in net gains from private equities , driven by company-specific events and corporate performance . net revenues in debt securities and loans were $ 1.51 billion , 9% ( 9 % ) lower than 2015 , reflecting significantly lower net revenues related to relationship lending activities , due to the impact of changes in credit spreads on economic hedges . losses related to these hedges were $ 596 million in 2016 , compared with gains of $ 329 million in 2015 . this decrease was partially offset by higher net gains from investments in debt instruments and higher net interest income . see note 9 to the consolidated financial statements for further information about economic hedges related to our relationship lending activities . operating expenses were $ 2.39 billion for 2016 , essentially unchanged compared with 2015 . pre-tax earnings were $ 1.69 billion in 2016 , 44% ( 44 % ) lower than 2015 . goldman sachs 2017 form 10-k 61 .