D. REVENUE

Our revenues are derived primarily from sales to customers in North America and Internationally, principally Europe. Net sales from these geographic markets, by segment, were as follows, in millions:



	Year Ended December 31, 2018
	Plumbing Products		Decorative Architectural Products		Cabinetry Products		Windows and Other Specialty Products		Total
Primary geographic markets:
North America	$	2,552	$	2,656	$	950	$	605	$	6,763
International, principally Europe	1,446		—		—		150		1,596
Total	$	3,998	$	2,656	$	950	$	755	$	8,359



	Year Ended December 31, 2017
	Plumbing Products		Decorative Architectural Products		Cabinetry Products		Windows and Other Specialty Products		Total
Primary geographic markets:
North America	$	2,362	$	2,206	$	891	$	608	$	6,067
International, principally Europe	1,370		—		43		162		1,575
Total	$	3,732	$	2,206	$	934	$	770	$	7,642



	Year Ended December 31, 2016
	Plumbing Products		Decorative Architectural Products		Cabinetry Products		Windows and Other Specialty Products		Total
Primary geographic markets:
North America	$	2,238	$	2,092	$	908	$	600	$	5,838
International, principally Europe	1,291		—		62		170		1,523
Total	$	3,529	$	2,092	$	970	$	770	$	7,361

We recognized increases to revenue of $4 million, $9 million, and $6 million in 2018, 2017, and 2016, respectively, for variable consideration related to performance obligations settled in previous periods.

We record contract assets for items for which we have satisfied our performance obligation but our receipt of payment is contingent upon delivery or other circumstances other than the passage of time. Our contract assets are recorded in prepaid expenses and other in our consolidated balance sheets. Our contract assets generally become unconditional and are reclassified to receivables in the quarter subsequent to each balance sheet date. Our contract asset balance was $14 million and $11 million at December 31, 2018 and 2017, respectively.

We record contract liabilities primarily for deferred revenue. Our contract liabilities are recorded in accrued liabilities in our consolidated balance sheets. Our contract liabilities are generally recognized to net sales in the immediately subsequent reporting period. Our contract liability balance was $41 million and $32 million at December 31, 2018 and 2017, respectively.