8.     CUSTOMER CONTRACTS, TRADENAMES AND TRADEMARKS, AND OTHER INTANGIBLE ASSETS

Customer contracts are amortized on a straight-line basis as this best approximates the ratio that current revenues bear to the total of current and anticipated revenues based on the estimated lives of the assets. In accordance with the FASB ASC Topic 350 “Intangibles - Goodwill and other”, the expected lives of customer contracts were analyzed, and it was determined that customer contracts should be amortized over a life of 7 to 20 years dependent upon customer type.

The carrying amount and accumulated amortization for customer contracts were as follows:

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The carrying amount of customer contracts as of December 31, 2021 reflects the impact of adjustments to correct prior periods. See Note 1, Basis of Presentation, for further information on the prior period adjustments recorded. The net carrying amount of customer contracts in foreign countries was $46.1 million as of December 31, 2022 and $42.1 million as of December 31, 2021.

Trademarks and tradenames are amortized on a straight-line basis over the period of their useful lives. The Company has determined these assets have useful lives between 7 and 20 years with non-amortizable, indefinite-lived tradenames of $104.3 million and $102.7 million as of December 31, 2022 and 2021, respectively.

The carrying amount and accumulated amortization for trademarks and tradenames were as follows:

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The net carrying amount of trademarks and tradenames in foreign countries was $4.2 million as of December 31, 2022 and $2.9 million as of December 31, 2021.

Other intangible assets include non-compete agreements and patents. Non-compete agreements are amortized on a straight-line basis over periods ranging from 3 to 20 years and patents are amortized on a straight-line basis over 15 years.

The carrying amount and accumulated amortization for other intangible assets were as follows:

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The net carrying amount of other intangible assets in foreign countries was $0.7 million as of December 31, 2022 and 2021.

Included in the table above are non-amortizable, indefinite-lived Internet domain names of $2.2 million at December 31, 2022 and 2021, respectively.

Total amortization expense was approximately $55.7 million in 2022, $46.0 million in 2021 and $38.7 million in 2020.

Estimated amortization expense for the existing carrying amount of customer contracts and other intangible assets for each of the five succeeding fiscal years are as follows:

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