Investments in affiliated companies that we do not control, either through majority ownership or otherwise, are accounted for using the equity method. At May 31, 2021, the Company held investments in the following affiliated companies: ArtiFlex Manufacturing, LLC (“ArtiFlex”) (50%), the Cabs joint venture (20%), Clarkwestern Dietrich Building Systems LLC (“ClarkDietrich”) (25%), Serviacero Planos, S. de R. L. de C.V. (“Serviacero Worthington”) (50%), and Worthington Armstrong Venture (“WAVE”) (50%)

On December 31, 2019, the Company contributed the then recently acquired operating net assets of Heidtman Steel Products, Inc.’s Cleveland facility (“Heidtman”) to the Samuel joint venture in exchange for an incremental 31.75% ownership interest in the Samuel joint venture, bringing our total ownership interest to 63%. The Samuel joint venture’s results have been consolidated within Steel Processing since that date. Refer to “Note Q – Acquisitions” for additional information.

On November 1, 2019, we closed on an agreement with an affiliate of Angeles Equity Partners, LLC by which we contributed substantially all of the net assets of our former Engineered Cabs business to a newly-formed joint venture, in exchange for a 20% noncontrolling interest. Immediately following the contribution, the Cabs joint venture acquired the net assets of Crenlo. Our contribution to the Cabs joint venture consisted of the net assets of our primary Engineered Cabs manufacturing facilities located in Greeneville, Tennessee and Watertown, South Dakota. Our investment in the Cabs joint venture is accounted for under the equity method due to lack of control.

During the fourth quarter of fiscal 2019, we determined our 10% ownership interest in our joint venture in China, Nisshin, was other than temporarily impaired due to then current and projected operating losses. As a result, in the fourth quarter of fiscal 2019, an impairment charge of $4,017,000 was recognized within equity income in our consolidated statement of earnings to write down the investment to its estimated fair value of $3,700,000. During the first quarter of fiscal 2020, the Company began the process of exploring the potential exit of its interest in the Nisshin joint venture in China. As a result, the Company evaluated its investment for potential impairment. The Company concluded the remaining book value of the investment was fully impaired, resulting in an impairment charge of $4,236,000 within equity income during the first quarter of fiscal 2020. On December 19, 2019, the Company finalized an agreement to transfer the risks and rewards related to its 10% interest to the other joint venture partners. As a result, the Company has no further rights or obligations related to the Nisshin joint venture.

We received distributions from unconsolidated affiliates totaling $91,007,000, $122,953,000, and $161,079,000 in fiscal 2021, fiscal 2020 and fiscal 2019, respectively. We have received cumulative distributions from WAVE in excess of our investment balance, which resulted in a negative asset balance of $99,669,000 and $103,837,000 at May 31, 2021 and 2020, respectively. In accordance with the applicable accounting guidance, we reclassified the negative balances to other liabilities within our consolidated balance sheets. We will continue to record our equity in the net income of WAVE as a debit to the investment account, and if it becomes positive, it will again be shown as an asset on our consolidated balance sheets. If it becomes probable that any excess distribution may not be returned (upon joint venture liquidation or otherwise), we will recognize any balance classified as a liability as income immediately.

The following table presents combined information regarding the financial position of our unconsolidated affiliates accounted for using the equity method as of May 31:

The following table presents summarized financial information for our four largest unconsolidated affiliates as of, and for the fiscal years ended May 31. All other unconsolidated affiliates are combined and presented in the Other category.

(in thousands)	2021			2020			2019
Net sales
WAVE	$	371,814		$	368,820		$	379,103
ClarkDietrich		893,371			855,994			892,758
Serviacero Worthington		311,543			273,276			351,671
ArtiFlex		144,834			175,428			201,526
Other		196,915			146,478			32,753
Total net sales	$	1,918,477		$	1,819,996		$	1,857,811

Gross margin (loss)
WAVE	$	215,692		$	208,040		$	205,909
ClarkDietrich		158,074			131,619			93,947
Serviacero Worthington		51,253			15,739			34,494
ArtiFlex		20,596			14,212			12,928
Other		(7,057	)		7,320			(6,000	)
Total gross margin	$	438,558		$	376,930		$	341,278

Operating income (loss)
WAVE	$	165,381		$	166,404		$	166,969
ClarkDietrich		94,888			66,952			33,384
Serviacero Worthington		43,075			7,513			25,636
ArtiFlex		9,628			6,248			5,524
Other		(2,372	)		(23,596	)		(9,964	)
Total operating income	$	310,600		$	223,521		$	221,549

Depreciation and amortization
WAVE	$	4,073		$	4,032		$	3,634
ClarkDietrich		11,917			11,869			11,600
Serviacero Worthington		4,305			4,324			4,319
ArtiFlex		5,728			5,605			6,055
Other		8,965			4,689			875
Total depreciation and amortization	$	34,988		$	30,519		$	26,483

Interest expense
WAVE	$	8,909		$	11,061		$	10,547
ClarkDietrich		101			378			912
Serviacero Worthington		42			87			493
ArtiFlex		528			801			1,443
Other		2,704			1,665			-
Total interest expense	$	12,284		$	13,992		$	13,395

Income tax expense (benefit)
WAVE	$	200		$	216		$	219
ClarkDietrich		-			-			-
Serviacero Worthington		11,341			3,267			7,629
ArtiFlex		149			(15	)		29
Other		270			(15	)		-
Total income tax expense	$	11,960		$	3,453		$	7,877

Net earnings (loss)
WAVE (1)	$	156,869		$	202,451		$	162,849
ClarkDietrich		98,313			68,899			34,560
Serviacero Worthington		31,865			2,573			16,155
ArtiFlex		8,950			5,461			4,051
Other		(2,811	)		(19,934	)		(8,383	)
Total net earnings	$	293,186		$	259,450		$	209,232

At May 31, 2021 and 2020, $59,015,000 and $39,995,000, respectively, of our consolidated retained earnings represented undistributed earnings of our unconsolidated affiliates, net of tax.