Revenue is recognized when control of the good or service is transferred to the customer either at a point in time or, in limited circumstances, as our services are rendered over time. Revenue is measured as the amount of consideration we expect to receive in exchange for transferring goods or services.

The following tables present net sales to external customers by reportable segment.



	Year Ended December 31, 2019
	Life Sciences		Mobile Solutions		Power Solutions		Intersegment Sales Eliminations			Total
United States	$	295,690	$	162,445	$	156,945	$	(2,130	)	$	612,950
China	7,330		38,793		6,722		—			52,845
Mexico	373		18,815		13,489		—			32,677
Brazil	3		36,058		300		—			36,361
Germany	29,239		6,372		65		—			35,676
Switzerland	14,016		4,340		57		—			18,413
Other	13,081		30,926		14,522		—			58,529
Total net sales	$	359,732	$	297,749	$	192,100	$	(2,130	)	$	847,451



	Year Ended December 31, 2018
	Life Sciences		Mobile Solutions		Power Solutions		Intersegment Sales Eliminations			Total
United States	$	206,776	$	187,178	$	157,357	$	(2,331	)	$	548,980
China	6,130		43,610		5,537		—			55,277
Mexico	191		27,053		12,254		—			39,498
Brazil	29		35,314		215		—			35,558
Germany	19,870		5,652		26		—			25,548
Switzerland	6,446		5,006		54		—			11,506
Other	8,731		31,224		14,335		—			54,290
Total net sales	$	248,173	335,037		189,778		(2,331		)	$	770,657



	Year Ended December 31, 2017
	Life Sciences		Mobile Solutions		Power Solutions		Intersegment Sales Eliminations			Total
United States	$	96,062	$	190,828	$	152,938	$	(1,990	)	$	437,838
China	267		45,503		6,481		—			52,251
Mexico	78		26,639		14,220		—			40,937
Brazil	—		35,425		185		—			35,610
Germany	35		5,502		11		—			5,548
Switzerland	—		5,450		—		—			5,450
Other	1,887		27,505		12,767		—			42,159
Total net sales	$	98,329	$	336,852	$	186,602	$	(1,990	)	$	619,793

Product Sales

We generally transfer control and recognize a sale when we ship the product from our manufacturing facility to our customer, at a point in time, as this is when our customer obtains the ability to direct use of, and obtain substantially all of the remaining benefits from, the goods. We have elected to recognize the cost for freight and shipping when control over products has transferred to the customer as a component of cost of sales.

We use an observable price to determine the stand-alone selling price for separate performance obligations or a cost-plus-margin approach when an observable price is not available. The expected duration of our contracts is one year or less, and we have elected to apply the practical expedient that allows entities to disregard the effects of financing when the contract length is less than one year. The amount of consideration we receive and the revenue we recognize varies with volume rebates and incentives we offer to our customers. We estimate the amount of variable consideration that should be included in the transaction price utilizing the expected value method or the most likely amount method depending on the nature of the variable consideration. Variable consideration is included in the transaction price if, in our judgment, it is probable that a significant future reversal of cumulative revenue under the contract will not occur.

We utilize the portfolio approach practical expedient to evaluate sales-related discounts on a portfolio basis to contracts with similar characteristics. The effect on our financial statements of applying the portfolio approach would not differ materially from applying the new standard to individual contracts.

We give our customers the right to return only defective products in exchange for functioning products or rework of the product. These transactions are evaluated and accounted for under ASC Topic 460, Guarantees, and we estimate the impact to the transaction price based on an analysis of historical experience.

Other Sources of Revenue

We provide pre-production activities related to engineering efforts to develop molds, dies, and machines that are owned by our customers. We may receive advance payments from customers which are deferred until satisfying our performance obligations by compliance with customer-specified milestones, recognizing revenue at a point in time. These contracts generally have an original expected duration of less than one year.

The following table provides information about contract liabilities from contracts with customers.



	Deferred Revenue
Balance at January 1, 2019	$	2,974
Balance at December 31, 2019	$	4,172

The timing of revenue recognition, billings, and cash collections results in billed accounts receivable and customer advances and deposits (e.g. contract liability) on the Consolidated Balance Sheets. These contract liabilities are reported on the Consolidated Balance Sheets on a contract-by-contract basis at the end of each reporting period as deferred revenue. Deferred revenue relates to payments received in advance of performance under the contract and recognized as revenue as (or when) we perform under the contract. Changes in the contract liability balances during the year ended December 31, 2019, were not materially impacted by any other factors. Revenue recognized for the year ended December 31, 2019, from amounts included in deferred revenue at the beginning of the period for performance obligations satisfied or partially satisfied during the period was $3.0 million.

Transaction Price Allocated to Future Performance Obligations

We are required to disclose the aggregate amount of transaction price that is allocated to performance obligations that have not yet been satisfied as of December 31, 2019, unless our contracts meet one of the practical expedients. Our contracts met the practical expedient for a performance obligation that is part of a contract that has an original expected duration of one year or less.

Costs to Obtain and Fulfill a Contract

We recognize commissions paid to internal sales personnel that are incremental to obtaining customer contracts as an expense when incurred since the amortization period is less than one year. The judgments made in determining the amount of costs incurred included whether the commissions are in fact incremental and would not have occurred absent the customer contract. Costs to obtain a contract are expensed as selling, general and administrative expense.

Sales, VAT, and other taxes we collect concurrent with revenue-producing activities are excluded from revenue. Incidental items that are immaterial in the context of the contract are recognized as expense.

Sales Concentration

For the year ended December 31, 2019, we recognized sales from a single customer of $93.1 million, or 11.0% of consolidated net sales. Revenues from this customer are in our Life Sciences and Power Solutions groups. No customers represented more than 10% of our net sales for the years ended December 31, 2018 and 2017. No customers represented more than 10% of accounts receivable as of December 31, 2019 or 2018.