8. Other Income

The components of other income for the years ended December 31, 2017, 2016, and 2015 were:



	Year-Ended December 31,
	2017		2016		2015
	(in millions)
Market data fees	$	39	$	35	$	30
Account activity fees		20		18		16
Risk exposure fees		24		19		21
Payments for order flow		15		14		17
Gains (losses) on financial instruments, at fair value and other investments, net		1		35		(18)
Gains (losses) from currency diversification strategy, net		110		(40)		(206)
Other, net		123		13		18
	$	332	$	94	$	(122)

Market data fees are charged to customers for market data services they subscribe to and are largely offset by the related costs paid to obtain market data from third party vendors. Account activity fees are charged to customers that do not generate the minimum monthly commission. The fee is the difference between the minimum required commission and the actual commissions generated. Risk exposure fees are earned from a small minority of customer accounts carrying positions with market risk that exceeds defined thresholds. Payments for order flow are earned from various options exchanges based upon options trading volume originated by the Operating Companies. Gains (losses) on financial instruments, at fair value and other investments, net include (1) realized and unrealized gains and losses on financial instruments that (a) are held for purposes other than the Company’s market making activities, (b) are subject to restrictions, or (c) are accounted for under the equity method and (2) dividends on investments accounted for under cost method. Other, net includes a gain on the sale of the Company’s U.S. market making operations to Two Sigma Securities, LLC of $11 million, reflecting the recovery of exit costs, and a $93 million gain from the remeasurement of the Tax Receivable Agreement liability as a result of the Tax Act (see Note 4 and Note 10).