16.COMMITMENTS AND CONTINGENCIES

Leases

The Company is obligated under various non-cancelable operating leases for land, office space, equipment and site leases that expire at various times through December 2152. In addition, the Company is obligated under various non-cancelable capital leases for vehicles that expire at various times through August 2022.

The annual minimum lease payments under non-cancelable operating (primarily ground or land leases) and capital leases for the next five years as of December 31, 2018 are as follows (in thousands):



For the year ended December 31,	Capital Leases		Operating Leases
2019	$	883	$	237,730
2020		482		239,208
2021		303		241,090
2022		86		242,320
2023		—		243,476
Total minimum lease payments		1,754
Less: amount representing interest		(83)
Present value of future payments		1,671
Less: current obligations		(860)
Long-term obligations	$	811

Future minimum rental payments under noncancelable ground leases include payments for certain renewal periods at the Company’s option because failure to renew could result in a loss of the applicable tower and related revenue from tenant leases, thereby making it reasonably assured that the Company will renew the lease. The majority of operating leases provide for renewal at varying escalations. Fixed rate escalations have been included in the table disclosed above.

Rent expense for operating leases was $273.5 million, $266.4 million and $253.7 million for the years ended December 31, 2018, 2017 and 2016, respectively. In addition, certain of the Company’s leases include contingent rent provisions which provide for the lessor to receive additional rent upon the attainment of certain tower operating results and/or lease-up. Contingent rent expense for the years ended December 31, 2018, 2017 and 2016 was $27.1 million, $26.6 million and $25.0 million, respectively.

Tenant Leases

The annual minimum tower lease income to be received for tower space and antenna rental under non-cancelable operating leases for the next five years as of December 31, 2018 is as follows:



For the year ended December 31,	(in thousands)
2019	$	1,529,902
2020		1,326,108
2021		1,075,675
2022		815,219
2023		598,987

The Company’s tenant leases provide for annual escalations and multiple renewal periods, at the tenant’s option. The tenant rental payments disclosed in the table above do not assume exercise of any tenant renewal options, however, fixed rate escalations have been included for the current term.

Litigation

The Company is involved in various claims, lawsuits and proceedings arising in the ordinary course of business. While there are uncertainties inherent in the ultimate outcome of such matters and it is impossible to presently determine the ultimate costs that may be incurred, management believes the resolution of such uncertainties and the incurrence of such costs will not have a material adverse effect on the Company’s consolidated financial position, results of operations or liquidity.

Contingent Purchase Obligations

From time to time, the Company agrees to pay additional consideration (or earnouts) for acquisitions if the towers or businesses that are acquired meet or exceed certain performance targets in the one to three years after they have been acquired. Please refer to Note 3.