The following summarizes property, equipment and software, net as of December 31, 2021 and 2020 (in thousands):


	December 31,
	2021		2020
Furniture and fixtures and other	5,524		5,681
Leasehold improvements	23,576		24,808
Computer hardware and purchased software	118,659		121,742
Internally-developed software (1)	309,018		264,103
Total property, equipment and software, gross	456,777		416,334
Less: accumulated depreciation and amortization	(383,196)		(331,050)
Property, equipment and software, net	$	73,581	$	85,284

(1)The net carrying amount of internally-developed software was $54.7 million and $57.9 million as of December 31, 2021 and 2020.

We recognized long-lived asset impairments during the third quarter 2021 for certain leasehold improvements under our restructuring plan and the first quarter 2020 for property, equipment and software, net, as described in Note 3, COVID-19 Pandemic. See Note 14, Restructuring and Related Charges, for more information on our restructuring impairments and details in the table below.

The asset impairments described above were written down to fair value based on the discounted cash flow method under the income approach that uses Level 3 inputs. The significant estimates used in the discounted cash flow models are the risk-adjusted discount rates; forecasted revenue, cost of revenue and operating expenses; forecasted capital expenditures and working capital needs; weighted-average cost of capital; rates of long-term growth; and income tax rates.

The following table summarizes impairment charges for property, equipment and software that are presented within Restructuring and related charges and Long-lived asset impairment on the consolidated statements of operations for the years ended December 31, 2021 and 2020 (in thousands):


	Year Ended December 31,
	2021		2020
Long-lived asset impairment:
North America	$	—	$	—
International	—		9,565
Long-lived asset impairment	—		9,565
Restructuring and related charges:
North America	602		—
International	268		5,613
Restructuring and related charges impairment	870		5,613
Total property, equipment and software impairment	$	870	$	15,178

The following table summarizes impairment for long-lived assets by asset type for the years ended December 31, 2021 and 2020 (in thousands):


	Year Ended December 31,
Long-Lived Asset Category	2021		2020
Property, equipment and software, net
Leasehold improvements	870		8,419
Computer hardware	—		2,842
Internally-developed software	—		2,988
Other Property, equipment and software, net	—		929
Total	$	870	$	15,178

Depreciation and amortization expense on property, equipment and software is classified as follows in the accompanying consolidated statements of operations for the years ended December 31, 2021, 2020 and 2019 (in thousands):


	Year Ended December 31,
	2021		2020		2019
Service cost of revenue	$	32,354	$	28,443	$	28,917
Product cost of revenue	378		9,434		6,466
Selling, general and administrative	31,193		39,915		56,027
Total	$	63,925	$	77,792	$	91,410

The above amounts include amortization of internally-developed software of $50.5 million, $58.8 million and $56.6 million, and amortization expense on assets under finance leases of $3.6 million, $6.7 million and $18.9 million, for the years ended December 31, 2021, 2020 and 2019.