Operating expenses

12 Months Ended

Dec. 31, 2020

Operating expenses

Operating expenses

7.     Operating expenses

Costs of services

Year ended December 31,	2020		2019		2018
Ancillary and logistical service expenses	$	59,982	$	59,252	$	66,576
Employee compensation expenses		47,745		50,093		41,391
Buildings, facilities and technology expenses		9,886		7,865		9,477
Travel, advertising and promotion expenses		22,636		31,652		27,606
Other costs of services		17,047		16,115		14,008
	$	157,296	$	164,977	$	159,058

SG&A expenses

Year ended December 31,	2020		2019		2018
Employee compensation expenses	$	286,908	$	246,028	$	249,115
Buildings, facilities and technology expenses		62,755		61,177		60,930
Travel, advertising and promotion expenses		25,780		38,248		36,728
Professional fees		18,220		15,572		16,768
Other SG&A expenses		23,860		21,364		19,135
	$	417,523	$	382,389	$	382,676

Acquisition-related costs

Acquisition-related costs consist of operating expenses directly incurred as part of our business combinations such as due diligence and integration planning related to our acquisitions, and share-based continuing employment costs. The following is a summary of our acquisition-related costs:

Year ended December 31,	2020		2019		2018
Rouse:
Share-based continuing employment costs	$	802	$	—	$	—
Other acquisition-related costs		5,212		—		—
		6,014		—		—
IronPlanet:
Other acquisition-related costs		—		82		2,944
Other acquisitions:
Continuing employment costs		—		128		2,091
Other acquisition-related costs		—		567		58
		—		777		5,093
	$	6,014	$	777	$	5,093

7.     Operating expenses (continued)

Depreciation and amortization expenses

Year ended December 31,	2020		2019		2018
Depreciation expense	$	31,330	$	29,112	$	29,021
Amortization expense		43,591		41,389		37,593
	$	74,921	$	70,501	$	66,614

During the year ended December 31, 2020, depreciation expense of $199,000 (2019: $410,000; 2018: $494,000) and amortization expense of $29,779,000 (2019: $27,944,000; 2018: $18,996,000) were recorded relating to software.