The activity in the accrued warranty liabilities account was as follows (in thousands):

	Six Months Ended
	June 29, 2019			June 30, 2018
Balance at beginning of year	$	10,389		$	9,320
Additions charged to costs and expenses for current-year sales		5,003			6,106
Deductions from reserves		(5,591	)		(5,790	)
Changes in liability for pre-existing warranties during the current year, including expirations		1,418			132
Balance at end of period	$	11,219		$	9,768

We are involved from time to time in various legal proceedings arising in the ordinary course of our business, including primarily commercial, product liability, employment and intellectual property claims. In accordance with U.S. generally accepted accounting principles, we record a liability in our consolidated financial statements with respect to any of these matters when it is both probable that a liability has been incurred and the amount of the liability can be reasonably estimated. If a loss is reasonably possible but not known or probable, and may be reasonably estimated, the estimated loss or range of loss is disclosed. With respect to currently pending legal proceedings, we have not established an estimated range of reasonably possible losses either because we believe that we have valid defenses to claims asserted against us or the proceeding has not advanced to a stage of discovery that would enable us to establish an estimate. We currently do not expect the outcome of pending legal proceedings to have a material effect on our consolidated results of operations, financial position or cash flows. Litigation, however, is inherently unpredictable, and it is possible that the ultimate outcome of one or more claims asserted against us could adversely impact our consolidated results of operations, financial position or cash flows. We expense legal costs as incurred.

On September 18, 2018, two former Home Delivery employees filed suit, now venued in Superior Court in Fresno County, California, alleging representative claims on a purported class action basis under the California Labor Code Private Attorney General Act. While the two representative plaintiffs were in the Home Delivery workforce, the Complaint does not limit the purported plaintiff class to that group. The plaintiffs allege that Sleep Number failed or refused to adopt adequate practices, policies and procedures relating to wage payments, record keeping, employment disclosures, meal and rest breaks, among other claims, under California law. The Complaint seeks damages in the form of civil penalties and plaintiffs’ attorneys’ fees, and expressly disclaims the recovery of any purported individual specific relief or underpaid wages. We intend to vigorously defend this matter.

On March 27, 2018, Level Sleep, LLC filed a patent infringement lawsuit against Sleep Number in the Federal District Court for the Eastern District of Texas. In its Complaint, Level Sleep claims that Sleep Number infringed two patents owned by Level Sleep, U.S. Patent Nos. 6,807,698 and 7,036,172 (the “Patents”), by, among other things, making, using, offering for sale, or selling within the United States, and/or importing into the United States, beds with sleep surfaces having foam with multiple zones in the longitudinal direction. Level Sleep has asserted that five non-360 beds no longer sold and two current non-360 beds infringe the Patents. Level Sleep seeks damages in the form of a reasonable royalty. Sleep Number has asserted that the Patents are invalid and that our products do not infringe the Patents. The case is scheduled for trial in February 2020 and is in the pre-trial discovery process. We intend to vigorously defend this matter.