Note 13. Revenues

Rents for 2016, 2015 and 2014, respectively, are comprised of the following:

	Years ended December 31,
	2016		2015		2014
Base rents	$	114,655,000	$	112,319,000	$	110,739,000
Percentage rent		654,000		789,000		683,000
Straight-line rents		38,000		506,000		761,000
Amortization of intangible lease liabilities, net		2,751,000		3,125,000		4,322,000
Total rents	$	118,098,000	$	116,739,000	$	116,505,000

Annual future base rents due to be received under non-cancelable operating leases in effect at December 31, 2016 are approximately as follows (excluding those base rents applicable to properties classified as real estate held for sale):

2017	$	101,880,000
2018		93,063,000
2019		79,220,000
2020		63,742,000
2021		49,311,000
Thereafter		213,217,000
	$	600,433,000

Total future minimum rents do not include expense recoveries for real estate taxes and operating costs, or percentage rents based upon tenants’ sales volume. Such additional revenue amounts aggregated approximately $32.7 million, $32.6 million and $32.1 million for 2016, 2015 and 2014, respectively. Such amounts do not include amortization of intangible lease liabilities.