The following table provides information about disaggregated revenue by primary geographical market and includes a reconciliation of the disaggregated revenue with reportable segments (in thousands):

	Three Months Ended March 31, 2019								Three Months Ended March 31, 2018
	Third-Party Software		Proprietary Software		Professional Engineering Service		Total		Third-Party Software		Proprietary Software		Professional Engineering Service		Total
Primary geographical markets:
North America	$	12,727	$	244	$	1,557	$	14,528	$	15,119	$	1,683	$	2,487	$	19,289
Europe		320		6		135		461		593		100		246		939
Asia		54		1		52		107		352		12		86		450
Total	$	13,101	$	251	$	1,744	$	15,096	$	16,064	$	1,795	$	2,819	$	20,678

We receive payments from customers based upon contractual billing schedules; accounts receivable is recorded when the right to consideration becomes unconditional. Contract assets include amounts related to our contractual right to consideration for completed performance obligations not yet invoiced and deferred contract acquisition costs, which are amortized over time as the associated revenue is recognized. Contract liabilities, presented as deferred revenue on our condensed consolidated balance sheets, include payments received in advance of performance under the contract and are realized when the associated revenue is recognized. We had asset impairment charges related to contract assets for each of the three months ended March 31, 2019 and 2018.

Significant changes in the contract assets and the deferred revenue balances during the three months ended March 31, 2019 were as follows (in thousands):

We capitalize contract acquisition costs for contracts with a life exceeding one year, as is more common with our DataV software bookings. Amortization of contract acquisition costs was $7,000 and $80,000 for the three months ended March 31, 2019 and 2018, respectively. There were no asset impairment charges for contract acquisition costs for any of the periods noted above.

The following table includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period (in thousands). The estimated revenue does not include contracts with original durations of one year or less, amounts of variable consideration attributable to royalties, or contract renewals that are unexercised as of March 31, 2019:

	Remainder of 2019		2020		2021		2022
Third-party software	$	37	$	14	$	—	$	—
Proprietary software		2,179		1,755		1,936		196
Professional engineering services		—		—		—		—

We apply a practical expedient and fully expense contract acquisition costs, such as sales commissions, as incurred because the amortization period is less than one year. We record these costs within selling, general and administrative expenses.