Selling, general and administrative expenses
Selling, general and administrative expenses from continuing operations increased $4.6 million, or 11%, and $7.8 million, or 6% during the three and nine months ended September 30, 2021, respectively, compared to the corresponding periods in 2020. The increases are primarily attributable to increases in marketing, compensation (including stock compensation), professional service and legal expenses, partially offset by decreases in costs associated with digital transformation initiatives.
Depreciation and amortization expenses
Depreciation and amortization expenses from continuing operations increased $4.1 million, or 11%, and $14.5 million, or 13%, during the three and nine months ended September 30, 2021, respectively, compared to the corresponding periods in 2020. The increases are primarily attributable to the timing of assets placed in service and increases in equipment and vehicle finance lease activity.
Interest expense
Interest expense decreased $9.8 million, or 30%, and $15.5 million, or 16%, during the three and nine months ended September 30, 2021, respectively, compared to the corresponding periods in 2020. The decreases are primarily due to the expiration of the interest rate swap agreement in May 2021 and repayment of approximately $1.1 billion of our long-term debt in September 2021.
Other income
Other income increased $1.0 million and $0.9 million during the three and nine months ended September 30, 2021, respectively, compared to the corresponding periods in 2020. The increases are primarily related to WOW entering into a Transition Services Agreement with Atlantic on September 1, 2021 to support post-transaction continuity of service during a transition period.
Discontinued Operations
On September 1, 2021, we sold our Cleveland and Columbus, Ohio markets to Atlantic for approximately $1.125 billion, subject to adjustments, including customary working capital adjustments, as specified in the Atlantic Purchase Agreement. For the three and nine months ended September 30, 2021, we recognized a gain on sale of $689.6 million resulting from the sale of our Cleveland and Columbus, Ohio markets.
Revenue from discontinued operations decreased $21.9 million, or 21%, and $18.1 million, or 6%, during the three and nine months ended September 30, 2021, respectively, compared to the corresponding periods in 2020. The decreases are primarily due to the completion of the sale of the Cleveland and Columbus, Ohio markets on September 1, 2021.
Operating expense for discontinued operations (excluding depreciation and amortization) decreased $11.4 million, or 28%, and $21.6 million, or 17%, during the three and nine months ended September 30, 2021, respectively, compared to the corresponding periods in 2020. The decreases are primarily due to the completion of the sale of the Cleveland and Columbus, Ohio markets on September 1, 2021, and the decrease in programming expense of $11.2 million and $20.4 million over the corresponding periods, respectively.
Discontinued operations expense does not include general corporate overhead or continuing costs related to providing service per the transition service agreements. Certain costs of providing the transition service agreements will continue during the term of the agreements as services are provided; however, upon termination of the agreements, these costs are expected to be reduced. In addition, general corporate overhead costs are expected to be reduced over a three year period.