The following table presents intangible assets as of:


	September 30, 2023					December 31, 2022
	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
	(in thousands)
Customer relationships	$	2,073,523	$	(835,594	)	$	2,029,955	$	(606,532	)
Trade names		64,500		(34,215	)		201,861		(164,797	)
Subcontractor relationships		—		—			5,440		(5,440	)
Non-compete agreements		13,050		(5,621	)		14,919		(5,685	)
Developed technology		95,600		(22,464	)		95,600		(14,377	)
Total intangible assets	$	2,246,673	$	(897,894	)	$	2,347,775	$	(796,831	)

In connection with the current year acquisitions, we recorded customer relationships intangible assets of $50.7 million. The weighted average useful life of the current year acquired intangible assets is 7.8 years. The fair value of acquired customer relationship intangible assets was primarily estimated by applying the multi-period excess earnings method, which involved the use of significant estimates and assumptions primarily related to forecasted revenue growth rates, gross margin, contributory asset charges, customer attrition rates, and market-participant discount rates. These measures are based on significant Level 3 inputs not observable in the market. Key assumptions developed based on the Company’s historical experience, future projections and comparable market data include future cash flows, long-term growth rates, attrition rates and discount rates.

During the three and nine months ended September 30, 2023, we recorded amortization expense in relation to the above-listed intangible assets of $83.5 million and $252.9 million, respectively. During the three and nine months ended September 30, 2022, we recorded amortization expense in relation to the above-listed intangible assets of $76.7 million and $212.5 million, respectively. During 2023, we derecognized certain customer relationships, trade names, non-compete agreements, and subcontractor relationships assets as they were fully amortized, resulting in a decrease in the gross carrying amount of the intangible assets and the related accumulated amortization.

The following table presents the estimated amortization expense for intangible assets for the years ending December 31:


	(in thousands)
2023 (from October 1, 2023)	$	81,680
2024		276,740
2025		201,748
2026		174,530
2027		148,947
Thereafter		465,134
Total future net intangible amortization expense	$	1,348,779