Investments in equity securities, by accounting classification, are summarized as follows:

(in millions)	June 30, 2022		December 31, 2021
Marketable equity securities	$	392	$	657
Non-marketable equity securities		511		441
Equity method investments		66		78
	$	969	$	1,176

(in millions)	Cost		Unrealized gains (losses)			Estimated fair value
June 30, 2022
Common stocks	$	374	$	4		$	378
Preferred stocks		16		(2	)		14
	$	390	$	2		$	392
December 31, 2021
Common stocks	$	418		222			640
Preferred stocks		17	$	—		$	17
	$	435	$	222		$	657

Net losses of $141 million and $206 million resulting from changes in the fair values of marketable equity securities were recognized for the three and six months ended June 30, 2022, respectively, which included net unrealized losses of $133 million and $198 million on securities still held at June 30, 2022, respectively. Included in net investment losses during the three and six months ended June 30, 2022, were unrealized losses of $92 million and $136 million, respectively, related to the Company’s investment in Offerpad Solutions Inc., a tech-enabled real estate company. Net gains of $24 million and $43 million resulting from changes in the fair values of marketable equity securities were recognized for the three and six months ended June 30, 2021, respectively, which included net unrealized gains of $24 million and $42 million on securities still held at June 30, 2021, respectively. Net gains and losses resulting from changes in the fair values of marketable equity securities are recognized in net investment gains/losses on the condensed consolidated statements of income.

(in millions)	Cost			Unrealized gains	Carrying amount
June 30, 2022	$	281	$	230	$	511
December 31, 2021	$	215	$	226	$	441

The Company recognized net unrealized gains of $15 million and $4 million during the three and six months ended June 30, 2022, respectively, and net unrealized gains of $44 million and $86 million during the three and six months ended June 30, 2021, respectively, related to its investments in private venture-stage companies. All such unrealized gains related to securities still held at June 30, 2022 and 2021. Net gains and losses on non-marketable equity securities are recognized in net investment gains/losses on the condensed consolidated statements of income.

During the six months ended June 30, 2022, the Company realized a gain of $51 million and cash proceeds of $63 million related to the sale of an investment in a title insurance business.