Page 129 - Martin Marietta - 2024 Proxy Statement

NOTES TO FINANCIAL STATEMENTS (Continued)
Intangible assets subject to amortization consist of the following:

Gross Accumulated Net
December 31 Amount Amortization Balance
(in millions) 2023
Noncompetition agreements $ 4.1 $ (4.1) $ —
Customer relationships 421.0 (79.9) 341.1
Operating permits 369.2 (55.8) 313.4
Use rights and other 14.2 (12.5) 1.7
Trade names 23.3 (15.9) 7.4
Total $ 831.8 $ (168.2) $ 663.6

2022
Noncompetition agreements $ 4.1 $ (4.0) $ 0.1
Customer relationships 423.7 (62.7) 361.0
Operating permits 502.2 (61.4) 440.8
Use rights and other 13.9 (12.4) 1.5
Trade names 23.3 (14.7) 8.6
Total $ 967.2 $ (155.2) $ 812.0

Intangible assets deemed to have an indefinite life that are therefore not amortized consist of the following:
Building
Materials Magnesia
December 31 Business Specialties Total
(in millions) 2023
Operating permits $ 6.6 $ — $ 6.6
Use rights 25.0 — 25.0
Trade names — 2.5 2.5
Total $ 31.6 $ 2.5 $ 34.1

2022
Operating permits $ 6.6 $ — $ 6.6
Use rights 26.7 — 26.7
Trade names — 2.5 2.5
Total $ 33.3 $ 2.5 $ 35.8

Amortization expense for intangible assets for the years ended December 31, 2023, 2022 and 2021 was $27.8 million, $26.6 million
and $24.0 million, respectively. The intangible assets with finite lives classified as held for sale are not being amortized.
The estimated amortization expense for intangible assets for each of the next five years and thereafter is as follows:
(in millions)
2024 $ 26.5
2025 26.4
2026 25.1
2027 24.5
2028 24.3
Thereafter 536.8
Total $ 663.6

23 Annual Report ♦ Page 27