PATENTS

Acacia’s only identifiable intangible assets at March 31, 2019 and December 31, 2018 are patents and patent rights. Patent-related accumulated amortization totaled $320,236,000 and $319,580,000 as of March 31, 2019 and December 31, 2018, respectively. Acacia’s patents have remaining estimated economic useful lives ranging from one to five years. The weighted-average remaining estimated economic useful life of Acacia’s patents is approximately four years.

The following table presents the scheduled annual aggregate amortization expense as of March 31, 2019 (in thousands):



For the years ending December 31,
Remainder of 2019	$	2,464
2020	2,421
2021	1,561
2022	1,561
2023	1,486
Thereafter	188
	$	9,681

For the three months ended March 31, 2019, Acacia accrued patent and patent rights acquisition costs totaling $3,750,000. The patents and patent rights acquired have estimated economic useful lives of approximately five years.