Insurance and claims decreased $3,452,000 in the 2021 thirteen-week period compared to the 2020 thirteen-week period and represented 11.4% of gross profit in the 2021 period compared to 17.5% of gross profit in the 2020 period. The decrease in insurance and claims expense compared to the prior year was primarily due to a severe claim incurred in the 2020 period, as well as the impact of net unfavorable development of prior years’ claims in the 2020 thirteen-week period, partially offset by an increase in insurance premiums, primarily for commercial trucking liability coverage. During the 2021 and 2020 thirteen-week periods, insurance and claims costs included $292,000 of net favorable and $2,223,000 of net unfavorable adjustments to prior years’ claims estimates, respectively. The decrease in insurance and claims as a percent of gross profit was caused by the effect of increased gross profit and the decrease in insurance and claims costs.
Selling, general and administrative costs increased $81,000 in the 2021 thirteen-week period compared to the 2020 thirteen-week period and represented 24.0% of gross profit in the 2021 period compared to 31.7% of gross profit in the 2020 period. The increase in selling, general and administrative costs compared to prior year was attributable to increased stock-based compensation expense, an increased provision for incentive compensation and increased wages, almost entirely offset by a decreased provision for customer bad debt, decreased employee benefit costs, decreased travel and entertainment costs and decreased event costs. Included in selling, general and administrative costs was stock-based compensation expense of $4,029,000 and $631,000 for the 2021 and 2020 thirteen-week periods, respectively, and incentive compensation expense of $4,289,000 and $2,031,000 for the 2021 and 2020 thirteen-week periods, respectively. The decrease in selling, general and administrative costs as a percent of gross profit was due to the effect of increased gross profit, partially offset by the increase in selling, general and administrative costs.
Depreciation and amortization increased $596,000 in the 2021 thirteen-week period compared to the 2020 thirteen-week period and represented 6.4% of gross profit in the 2021 period compared to 8.0% of gross profit in the 2020 period. The increase in depreciation and amortization expenses was primarily due to increased depreciation on information technology assets. The decrease in depreciation and amortization as a percentage of gross profit was due to the effect of increased gross profit, partially offset by the increase in depreciation and amortization.
Interest and debt expense in the 2021 thirteen-week period increased $90,000 compared to the 2020 thirteen-week period. The increase in interest and debt expense was primarily attributable to decreased interest income earned on cash balances held by the transportation logistics segment.
The provisions for income taxes for the 2021 and 2020 thirteen-week periods were based on estimated annual effective income tax rates of 24.4% and 24.2%, respectively, adjusted for discrete events, such as benefits resulting from stock-based awards. The increase in the estimated annual effective income tax rate was primarily attributable to an increased provision for nondeductible executive compensation during the 2021 period. The effective income tax rate for the 2021 thirteen-week period was 24.4%, which was higher than the statutory federal income tax rate of 21% primarily attributable to state taxes and nondeductible executive compensation, partially offset by excess tax benefits realized on stock based awards. The effective income tax rate for the 2020 thirteen-week period was 22.9%, which was higher than the statutory federal income tax rate of 21% primarily attributable to state taxes and the meals and entertainment exclusion, partially offset by excess tax benefits realized on stock based awards. The effective income tax rate in the 2020 thirteen-week period of 22.9% was lower than the 24.2% estimated annual effective income tax rate primarily due to excess tax benefits recognized on stock-based compensation arrangements in the 2020 thirteen-week period.
Net income was $77,240,000, or $2.01 per common share ($2.01 per diluted share), in the 2021 thirteen-week period. Net income was $40,895,000, or $1.04 per common share ($1.04 per diluted share), in the 2020 thirteen-week period.
CAPITAL RESOURCES AND LIQUIDITY
Working capital and the ratio of current assets to current liabilities were $474,654,000 and 1.7 to 1, respectively, at March 27, 2021, compared with $402,038,000 and 1.5 to 1, respectively, at December 26, 2020. Landstar has historically operated with current ratios within the range of 1.5 to 1 to 2.0 to 1. Cash provided by operating activities was $69,891,000 in the 2021 thirteen-week period compared with $99,216,000 in the 2020 thirteen-week period. The decrease in cash flow provided by operating activities was primarily attributable to the 39% increase in revenue year-over-year, which increased net receivables, defined as accounts receivable less accounts payable.
The Company declared and paid $0.21 per share, or $8,067,000 in the aggregate, in cash dividends during the thirteen-week period ended March 27, 2021 and, during such period, also paid $76,770,000 of dividends payable which were declared during fiscal year 2020 and included in current liabilities in the consolidated balance sheet at December 26, 2020. The Company declared and paid $0.185 per share, or $7,336,000 in the aggregate, in cash dividends during the thirteen-week period ended March 28, 2020 and, during such period, also paid $78,947,000 of dividends payable which were declared during fiscal year 2019 and included in current liabilities in the consolidated balance sheet at December 28, 2019. During the thirteen-week period ended March 27, 2021, the Company did not purchase any shares of its common stock. During the thirteen-week period ended March 28, 2020, the Company purchased 1,178,970 shares of its common stock at a total cost of $115,962,000. As of March 27, 2021, the Company may purchase in the aggregate up to 1,821,030 shares of its common stock under its authorized stock purchase program. Long-term debt, including current maturities, was $90,996,000 at March 27, 2021, $9,778,000 lower than at December 26, 2020.