Operating segments are defined as components of an enterprise that engage in business activities that earn revenue, incur expenses, and prepare separate financial information that is evaluated regularly by our chief operating decision maker in order to allocate resources and assess performance. During the quarter ended December 31, 2018, we changed our segment presentation to reflect the reorganization of our Oil and Gas Proppants and frac sand distribution businesses. Under this reorganization, the distribution business, which was acquired in fiscal 2018, became a division of the Oil and Gas Proppants business. The operations of the frac sand distribution business had previously been reported in the Other segment. For comparative purposes, we have adjusted the prior period segment presentation to reflect this change.

We are a leading supplier of heavy construction materials, light building materials, and materials used for oil and natural gas extraction in the United States. Our products are commodities that are essential in commercial and residential construction; public construction projects; projects to build, expand, and repair roads and highways; and in oil and natural gas extraction.

Our business is organized into three sectors within which there are five reportable business segments. The Heavy Materials sector includes the Cement and Concrete and Aggregates segments. The Light Materials sector includes the Gypsum Wallboard and Recycled Paperboard segments. The Oil and Gas Proppants segment produces frac sand used in oil and gas extraction.

Our business activities are conducted in the U.S. and include the mining of limestone for the manufacture, production, distribution, and sale of portland cement (a basic construction material which is the essential binding ingredient in concrete) and specialty oil well cement; the grinding and sale of slag cement; the mining of gypsum, for the manufacture and sale of gypsum wallboard; the manufacture and sale of recycled paperboard to the gypsum wallboard industry and other paperboard converters; the sale of readymix concrete; and the mining and sale of aggregates (crushed stone, sand, and gravel) and sand used in hydraulic fracturing (frac sand).

We operate seven cement plants, one slag grinding facility, 19 cement distribution terminals, five gypsum wallboard plants, a recycled paperboard mill, 17 readymix concrete batch plants, four aggregates processing plants, two frac sand processing facilities, four frac sand drying facilities, and five frac sand trans-load locations. The principal markets for our cement products are Texas, Illinois, the central plains, Michigan, Iowa, the Rocky Mountains, northern Nevada, southern Ohio, and northern California. Gypsum wallboard and recycled paperboard are distributed throughout the continental U.S., with the exception of the Northeast. Concrete and aggregates are sold to local readymix producers and paving contractors in the Austin, Texas area; north of Sacramento, California; and the greater Kansas City, Missouri area, while frac sand is currently sold into shale deposits across the United States.

We conduct one of our seven cement plant operations, Texas Lehigh Cement Company LP in Buda, Texas, through a Joint Venture. For segment reporting purposes only, we proportionately consolidate our 50% share of the Joint Venture’s Revenue and Operating Earnings, consistent with the way management reports the segments within the Company for making operating decisions and assessing performance.

We account for intersegment sales at market prices. The table below sets forth certain financial information relating to our operations by segment. We do not allocate interest or taxes at the segment level, only at the consolidated company level.

	For the Years Ended March 31,
	2019			2018			2017
	(dollars in thousands)
Revenue -
Cement	$	656,759		$	651,750		$	566,321
Concrete and Aggregates		140,173			157,013			154,592
Gypsum Wallboard		532,712			491,779			473,651
Paperboard		167,656			181,742			167,065
Oil and Gas Proppants		82,987			98,244			34,623
		1,580,287			1,580,528			1,396,252
Less: Intersegment Revenue		(82,553	)		(88,124	)		(79,116	)
Less: Joint Venture Revenue		(104,493	)		(105,884	)		(105,916	)
	$	1,393,241		$	1,386,520		$	1,211,220

	For the Years Ended March 31,
	2019		2018		2017
	(dollars in thousands)
Intersegment Revenue -
Cement	$	14,408	$	16,442	$	15,781
Concrete and Aggregates		1,422		1,335		1,262
Paperboard		66,723		70,347		62,073
	$	82,553	$	88,124	$	79,116
Cement Sales Volume (M tons) -
Wholly Owned		4,441		4,453		3,934
Joint Venture		899		912		937
		5,340		5,365		4,871

	For the Years Ended March 31,
	2019				2018			2017
				(dollars in thousands)
Operating Earnings -
Cement	$	164,782			$	179,151		$	153,525
Concrete and Aggregates		12,866				17,854			18,072
Gypsum Wallboard		180,831				158,551			159,866
Paperboard		35,349				32,758			37,601
Oil and Gas Proppants		(28,695	)			(6,139	)		(14,633	)
Sub-Total		365,133				382,175			354,431
Corporate General and Administrative Expense		(37,371	)			(41,205	)		(33,940	)
Impairment Losses		(220,265	)			—			—
Litigation Settlements and Losses		(1,800	)			(45,098	)		—
Other Non-Operating Income		2,412				3,728			2,139
Acquisition and Litigation Expense		—				—			(5,480	)
Earnings Before Interest and Income Taxes		108,109				299,600			317,150
Interest Expense, net		(28,374	)			(27,638	)		(22,631	)
Earnings Before Income Taxes	$	79,735			$	271,962		$	294,519
Cement Operating Earnings -
Wholly Owned	$	126,217			$	135,732		$	111,139
Joint Ventures		38,565				43,419			42,386
	$	164,782			$	179,151		$	153,525
Capital Expenditures -
Cement	$	76,504			$	45,088		$	32,790
Concrete and Aggregates		6,649				4,977			6,528
Gypsum Wallboard		10,724				19,382			11,393
Paperboard		16,603				5,177			3,996
Oil and Gas Proppants		52,286				56,872			1,534
Other, net		6,107				461			697
	$	168,873			$	131,957		$	56,938
Depreciation, Depletion and Amortization -
Cement	$	52,802			$	50,891		$	36,727
Concrete and Aggregates		8,176				7,931			7,931
Gypsum Wallboard		20,020				18,179			18,728
Paperboard		8,541				8,694			8,425
Oil and Gas Proppants		31,328				26,872			18,255
Corporate and Other		1,668				1,448			1,725
	$	122,535			$	114,015		$	91,791

	As of March 31,
	2019		2018		2017
	(dollars in thousands)
Identifiable Assets
Cement	$	1,289,468	$	1,247,504	$	1,234,617
Concrete and Aggregates		95,084		104,851		110,413
Gypsum Wallboard		372,206		386,041		379,414
Paperboard		138,614		123,819		124,356
Oil and Gas Proppants		236,357		444,826		376,306
Other, net		37,434		60,962		22,018
	$	2,169,163	$	2,368,003	$	2,247,124

Segment Operating Earnings, including the proportionately consolidated 50% interest in the revenue and expenses of the Joint Venture, represent Revenue less direct operating expenses, segment Depreciation, and segment Selling, General, and Administrative expenses. Segment Operating Earnings don’t include certain non-recurring losses, such as impairment and legal settlements. We account for intersegment sales at market prices. Corporate assets consist primarily of cash and cash equivalents, general office assets, and miscellaneous other assets.

The basis used to disclose Identifiable Assets; Capital Expenditures; and Depreciation, Depletion, and Amortization conforms with the equity method, and is similar to how we disclose these accounts in our Consolidated Balance Sheets and Consolidated Statements of Earnings.

Summarized financial information for the Joint Venture that is not consolidated is set out below (this summarized financial information includes the total amount for the Joint Venture and not our 50% interest in those accounts.)