4. Goodwill and Intangible Assets

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The changes in the carrying value of goodwill by segment for the six-month period ended December 31, 2022 were as follows (in thousands)

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Intangible assets consisted of the following (in thousands):

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Amortization expense related to intangible assets was $4.2 million and $4.8 million for the three months ended December 31, 2021 and 2022, respectively. For the six months ended December 31, 2021 and 2022, amortization expense related to intangible assets was $8.6 million and $9.4 million, respectively.

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At December 31, 2022, the estimated future amortization expense for intangible assets was as follows (in thousands):

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Fiscal Year

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Software development costs for software products incurred before establishing technological feasibility are charged to operations. Software development costs incurred after establishing technological feasibility are capitalized on a product-by-product basis until the product is available for general release to customers at which time amortization begins. Annual amortization, charged to cost of goods sold, is the amount computed using the ratio that current revenues for a product bear to the total current and anticipated future revenues for that product. In the event that future revenues are not estimable, such costs are amortized on a straight-line basis over the remaining estimated economic life of the product. Amortizable assets that have not yet begun to be amortized are included in Thereafter in the table above. For the three months ended December 31, 2021 and 2022, we capitalized software development costs in the amounts of $3.6 million and $4.0 million, respectively. For the six months ended December 31, 2021 and 2022, we capitalized software development costs in the amounts of $7.7 million and $7.9 million, respectively.