6. Intangible Assets

In connection with the current year acquisitions, we recorded customer relationships intangible assets of $37.7 million. The weighted average useful life of the current year acquired intangible assets is 2.9 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 six months ended June 30, 2024, we recorded amortization expense in relation to the above-listed intangible assets of $81.0 million and $160.9 million, respectively. During the three and six months ended June 30, 2023, we recorded amortization expense in relation to the above-listed intangible assets of $84.8 million and $169.4 million, respectively.