We test goodwill for impairment at least annually and on an interim basis if an event or circumstance indicates that it is more likely than not that an impairment loss has been incurred. During the second quarter of 2021, we completed the annual goodwill impairment assessment, on a quantitative basis, for goodwill for each of our three reporting units. The result of our annual assessment was that the fair value of the North America, International and EMEA reporting units exceeded their carrying values as of our measurement date of May 31, 2021 and we concluded that no impairment existed.

Estimating the fair value of each reporting unit requires us to make assumptions and estimates regarding our future. We utilized a combination of both a discounted cash flows and market approach. The financial projections used in the valuation models reflected management's assumptions regarding revenue growth rates, economic and market trends, cost structure, and other expectations about the anticipated short-term and long-term operating results for each of our three reporting units.

In management’s opinion, the goodwill balance for our ACCO Brands International reporting unit could be at risk for impairment if operating performance does not continue to recover as expected from the current impacts of COVID-19, if we experience negative changes to the long-term outlook for the business, or if changes in factors and assumptions occur which impact the fair value such as low or declining revenue growth rates, depressed operating margins or adverse changes to the discount rates impacting this reporting unit.

Changes in the net carrying amount of goodwill by segment were as follows:


(in millions)		ACCO Brands North America			ACCO Brands EMEA				ACCO Brands International			Total
Balance at December 31, 2021	$		446.7	$		178.6		$		177.2	$		802.5
Foreign currency translation			—			(5.2	)			1.6			(3.6	)
Balance at March 31, 2022	$		446.7	$		173.4		$		178.8	$		798.9

The goodwill balance includes $215.1 million of accumulated impairment losses, which occurred prior to December 31, 2016.

The gross carrying value and accumulated amortization by class of identifiable intangible assets as of March 31, 2022 and December 31, 2021, were as follows:


		March 31, 2022										December 31, 2021
(in millions)		Gross Carrying Amounts			Accumulated Amortization				Net Book Value			Gross Carrying Amounts			Accumulated Amortization				Net Book Value
Indefinite-lived intangible assets:
Trade names(1)	$		415.8	$		(44.5	)	$		371.3	$		417.6	$		(44.5	)	$		373.1
Amortizable intangible assets:
Trade names			381.2			(114.7	)			266.5			373.2			(110.5	)			262.7
Customer and contractual relationships			366.5			(188.7	)			177.8			366.5			(182.4	)			184.1
Vendor relationships			82.4			(7.1	)			75.3			82.4			(5.7	)			76.7
Patents			8.4			(3.2	)			5.2			8.6			(3.0	)			5.6
Subtotal			838.5			(313.7	)			524.8			830.7			(301.6	)			529.1
Total identifiable intangibles	$		1,254.3	$		(358.2	)	$		896.1	$		1,248.3	$		(346.1	)	$		902.2

(1)

Accumulated amortization prior to the adoption of authoritative guidance on goodwill and other intangible assets, at which time further amortization ceased.

The Company's intangible amortization expense for the three months ended March 31, 2022 and 2021 was $11.1 million and $12.0 million, respectively.

Estimated amortization expense for amortizable intangible assets, as of March 31, 2022, for the current year and the next five years is as follows:


(in millions)		2022			2023			2024			2025			2026			2027
Estimated amortization expense(2)	$		42.8	$		40.5	$		38.8	$		37.2	$		35.1	$		31.9

(2)

Actual amounts of amortization expense may differ from estimated amounts due to changes in foreign currency exchange rates, additional intangible asset acquisitions, impairment of intangible assets, accelerated amortization of intangible assets and other events.

We test indefinite-lived intangibles for impairment at least annually and on an interim basis if an event or circumstance indicates that it is more likely than not that an impairment loss has been incurred. We performed this annual assessment, on a quantitative basis, for our indefinite-lived trade names and concluded that no impairment existed as of our measurement date of May 31, 2021.

The result of our impairment testing of our indefinite-lived intangible assets determined the fair value of our five indefinite-lived trade names ACCO Brands®, Five Star®, Swingline®, Leitz® and Tilibra® exceeded their carrying values. The fair value of these trade names are considered Level 3 measurements which utilize a relief-from-royalty discounted cash flows approach. Key inputs and assumptions involved include the estimated near-term revenue growth, long-term growth rate, royalty rate, and discount rate.

As of May 31, 2021, we changed the indefinite-lived Tilibra® trade name to an amortizable intangible asset. The change was made as a result of decisions regarding the Company's future use of the trade name. The Company began amortizing the Tilibra® trade name on a straight-line basis over a life of 30 years effective June 1, 2021.