Years Ended December 31,
2019
2018
Deferred tax assets
Stock based compensation
$1,757
$1,337
Net operating loss and tax credit carryforwards
86,879
38,622
Interest expense limitation
7,620
—
Pension obligation
13,473
3,302
Excess and obsolete inventory
3,217
2,161
Deferred revenue
3,305
6,903
Employee bonuses and commissions
2,537
1,874
Depreciation and amortization
29,015
29,525
Operating lease liabilities
23,451
—
Other
9,685
9,961
Deferred tax assets
180,939
93,685
Less: Valuation allowance
(76,206)
(30,924)
Net deferred tax assets
104,733
62,761
Deferred tax liabilities
Depreciation and amortization
41,549
17,723
Unremitted earnings
4,740
3,529
Operating lease right-of-use assets
22,774
—
Other
2,966
1,267
Deferred tax liabilities
72,029
22,519
Net deferred tax assets
$32,704
$40,242

text: ADVANCED ENERGY INDUSTRIES, INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS – (continued) (in thousands, except per share amounts)
text: Deferred tax assets and liabilities are recognized for the future tax consequences of differences between the carrying amounts of assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to be reversed. Significant deferred tax assets and liabilities consist of the following:
text: Of the $32.7 million and $40.2 million net deferred tax asset at December 31, 2019 and 2018, respectively, $42.7 million and $47.1 million is reflected as a net non-current deferred tax asset and $10.0 million and $7.0 million is reflected as a long-term liability at December 31, 2019 and 2018, respectively.
text: As of December 31, 2019, the Company has recorded a valuation allowance on $16.0 million of its U.S. domestic deferred tax assets, largely attributable to acquired federal capital loss carryforwards for which the Company does not have sufficient income in the character to realize that attribute, and state carryforward attributes that are expected to expire before sufficient income can be realized in those jurisdictions. The remaining valuation allowance on deferred tax assets approximates $60.2 million and is associated primarily with operations in Austria, Germany, Hong Kong and Switzerland. As of December 31, 2019, there is not sufficient positive evidence to conclude that such deferred tax assets, presently reduced by a valuation allowance, will be recognized. The December 31, 2019 valuation allowance balance reflects an increase of $45.3 million during the year. The change in the valuation allowance is primarily due to increases from acquired Artesyn positions and current year activity, partially offset by decreases due to foreign exchange movements

Questions:
question: How much was reflected as a long-term liability in 2018?
answer: $7.0 million
scale: million
question: What was the stock based compensation in 2019?
answer: $1,757
scale: thousand
question: What was the Net operating loss and tax credit carryforwards in 2018?
answer: 38,622
scale: thousand
question: What was the change in pension obligation between 2018 and 2019?
answer: 10171
derivation: 13,473-3,302
scale: thousand
question: What was the change in Excess and obsolete inventory between 2018 and 2019?
answer: 1056
derivation: 3,217-2,161
scale: thousand
question: What was the percentage change in Net deferred tax assets between 2018 and 2019?
answer: -18.73
derivation: ($32,704-$40,242)/$40,242
scale: percent