3.	Financial Instruments Measured at Fair Value

Our cash, cash equivalents, and short-term investments consisted primarily of cash and other investment grade securities. We do not hold investment securities for trading purposes. All short-term investments are classified as available-for-sale and recorded at fair value. Investment securities are exposed to market risk due to changes in interest rates and credit risk and we monitor credit risk and attempt to mitigate exposure by making high-quality investments and through investment diversification.

Gains and losses on investments are calculated using the specific-identification method and are recognized during the period in which the investment is sold or when an investment experiences an other-than-temporary decline in value. Factors that could indicate an impairment exists include, but are not limited to: earnings performance, changes in credit rating or adverse changes in the regulatory or economic environment of the asset. Gross realized gains and losses on sales of short-term investments are included in interest income. Realized gains and losses for the periods presented were not significant.

Investments that we have classified as short-term, by security type, are as follows

(

in thousands

)

	March 25, 2017
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	12,306	$	1	$	2	$	12,305
Government-sponsored enterprise securities		8,701		-		3		8,698
Bank certificates of deposit		750		1		-		751
Foreign government security		615		-		-		615
	$	22,372	$	2	$	5	$	22,369

	December 31, 2016
			Gross		Gross		Estimated
	Amortized		Unrealized		Unrealized		Fair
	Cost		Gains		Losses (1)		Value
Corporate debt securities (2)	$	22,513	$	1	$	6	$	22,508
Government-sponsored enterprise securities		8,109		-		1		8,108
Bank certificates of deposit		750		1		-		751
Foreign government security		623		-		-		623
	$	31,995	$	2	$	7	$	31,990

(1)

As of

March

25,

2017

there were

$18.5

million of investments in our portfolio in a loss position. As of

December

31,

2016

the cost and fair value of investments with loss positions were approximately

$26.6

million. We evaluated the nature of these investments, credit worthiness of the issuer and the duration of these impairments to determine if an other-than-temporary decline in fair value had occurred and concluded that these losses were temporary and we have the ability and intent to hold these investments to maturity.

(2)

Corporate debt securities include investments in financial and other corporate institutions. No single issuer represents a significant portion of the total corporate debt securities portfolio.

Effective maturities of short-term investments are as follows

(in thousands)

	March 25, 2017				December 31, 2016
	Amortized		Estimated		Amortized		Estimated
	Cost		Fair Value		Cost		Fair Value
Due in one year or less	$	21,757	$	21,754	$	31,372	$	31,367
Due after one year through three years		615		615		623		623
	$	22,372	$	22,369	$	31,995	$	31,990

Accounting standards pertaining to fair value measurements establish a

three

-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level

defined as observable inputs such as quoted prices in active markets; Level

defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level

defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. When available, we use quoted market prices to determine the fair value of our investments, and they are included in Level

When quoted market prices are unobservable, we use quotes from independent pricing vendors based on recent trading activity and other relevant information, and they are included in Level

The following table summarizes, by major security type, our financial instruments that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy

(in thousands)

	Fair value measurements at March 25, 2017 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	57,777	$	-	$	-	$	57,777
Corporate debt securities		-		20,500		-		20,500
Government-sponsored enterprise securities		-		8,698		-		8,698
Money market funds		-		17,864		-		17,864
Bank certificates of deposit		-		751		-		751
Foreign government security		-		615		-		615
	$	57,777	$	48,428	$	-	$	106,205

	Fair value measurements at December 31, 2016 using:
							Total estimated
	Level 1		Level 2		Level 3		fair value
Cash	$	70,279	$	-	$	-	$	70,279
Foreign government security		-		623		-		623
Corporate debt securities		-		24,108		-		24,108
Government-sponsored enterprise securities		-		8,108		-		8,108
Money market funds		-		24,166		-		24,166
Bank certificates of deposit		-		751		-		751
	$	70,279	$	57,756	$	-	$	128,035