Selling, general and administrative expenses. SG&A expenses increased $8.7 million, or 7.5%, to $124.0 million for the thirteen weeks ended December 30, 2023 from $115.3 million for the thirteen weeks ended December 24, 2022. The increase in SG&A expenses as compared to the prior-year period was primarily a result of higher general and administrative expenses, store payroll associated with operating 49 new stores and other operating expenses in the current year. As a percentage of net sales, SG&A increased by 140 basis points to 23.8% for the thirteen weeks ended December 30, 2023 from 22.4% for the thirteen weeks ended December 24, 2022 primarily as a result of higher overhead, payroll and other operating expenses.
Income from operations. Income from operations increased $2.6 million, or 3.7%, to $75.1 million for the thirteen weeks ended December 30, 2023 from $72.5 million for the thirteen weeks ended December 24, 2022. The increase in income from operations was attributable to the factors noted above. As a percentage of net sales, income from operations was 14.4% and 14.1% for the thirteen weeks ended December 30, 2023 and December 24, 2022, respectively.
Interest expense. Interest expense was $0.5 million and $2.3 million for the thirteen weeks ended December 30, 2023 and December 24, 2022, respectively. The decrease in interest expense in the current-year period was primarily the result of a lower debt balance in the current year, partially offset by a higher weighted average interest rate compared to the prior-year period.
Income tax expense. Income tax expense was $19.4 million for the thirteen weeks ended December 30, 2023, compared to $17.5 million for the thirteen weeks ended December 24, 2022. Our effective tax rate was 25.8% and 24.9% for the thirteen weeks ended December 30, 2023 and December 24, 2022, respectively. The tax rate for the thirteen weeks ended December 30, 2023 was higher than the tax rate for the thirteen weeks ended December 24, 2022, primarily due to changes to state enacted tax rates, partially offset by a higher tax benefit due to income tax accounting for share-based compensation compared to the thirteen weeks ended December 24, 2022.
Net income. Net income was $55.6 million for the thirteen weeks ended December 30, 2023 compared to $52.8 million for the thirteen weeks ended December 24, 2022. The increase in net income was primarily attributable to the factors noted above.
Thirty-Nine Weeks Ended December 30, 2023 Compared to Thirty-Nine Weeks Ended December 24, 2022
Net sales. Net sales increased $46.6 million, or 3.8%, to $1.279 billion for the thirty-nine weeks ended December 30, 2023 from $1.232 billion for the thirty-nine weeks ended December 24, 2022. Consolidated same store sales decreased 6.3%. Excluding the impact of the 11.4% decrease in e-commerce same store sales, same store sales decreased by 5.6%. The increase in net sales was the result of the incremental sales from new stores opened over the past twelve months, partially offset by the decrease in consolidated same store sales.
Gross profit. Gross profit increased $20.3 million, or 4.5%, to $475.0 million for the thirty-nine weeks ended December 30, 2023 from $454.7 million for the thirty-nine weeks ended December 24, 2022. As a percentage of net sales, gross profit was 37.2% and 36.9% for the thirty-nine weeks ended December 30, 2023 and December 24, 2022, respectively. Gross profit increased primarily due to sales growth and merchandise margin expansion. The increase in gross profit rate of 30 basis points was driven primarily by a 170 basis-point increase in merchandise margin rate, partially offset by 140 basis points of deleverage in buying, occupancy and distribution center costs. The increase in merchandise margin rate was driven by a 120 basis-point improvement in freight expense as a percentage of net sales and 50 basis points of product margin expansion resulting primarily from growth in exclusive brand penetration. The deleverage in buying, occupancy and distribution center costs was driven primarily by the occupancy costs of 49 new stores and operating costs related to the new Kansas City distribution center.
Selling, general and administrative expenses. SG&A expenses increased $29.3 million, or 10.3%, to $315.0 million for the thirty-nine weeks ended December 30, 2023 from $285.7 million for the thirty-nine weeks ended December 24, 2022. The increase in SG&A expenses as compared to the prior-year period was primarily a result of higher store payroll and store-related expenses associated with operating 49 new stores and general and administrative expenses in the current year. As a percentage of net sales, SG&A increased by 140 basis points to 24.6% for the thirty-nine weeks ended