4. Acquired Intangible Assets and Liabilities

The gross above-market lease value at December 31, 2015, and 2014, was $2.2 million and $2.7 million, respectively, and total accumulated amortization at December 31, 2015, and 2014, was $1.8 million and $1.9 million, respectively. The gross below-market lease value at December 31, 2015, and 2014, was $10.0 million and $10.3 million, respectively, and total accumulated amortization at December 31, 2015, and 2014, was $5.3 million and $4.7 million, respectively. The net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental revenue of $0.5 million, $0.6 million, and $0.8 million, for the years ended December 31, 2015, 2014, and 2013, respectively. The estimated amortization of acquired below-market leases, net of acquired above-market leases for each of the five succeeding fiscal years, which will be a net increase to rental revenue, is as follows (in thousands):

Year Ending December 31,
2016	$	541
2017		572
2018		573
2019		245
2020		136
Thereafter		2,195

Total	$	4,262

Amortization of all other identified intangible assets was $2.0 million, $3.4 million, and $7.4 million, for the years ended December 31, 2015, 2014, and 2013, respectively. At December 31, 2015, and 2014, the gross intangible asset values were $14.0 million and $18.8 million, respectively, and the total accumulated amortization balance was $9.7 million and $12.5 million, respectively. The estimated amortization of all other identified intangible assets for each of the five succeeding fiscal years is as follows (in thousands):

Year Ending December 31,
2016	$	1,630
2017		1,136
2018		621
2019		316
2020		115
Thereafter		457

Total	$	4,275