and the average health, welfare, and pension benefit contribution rate increased approximately 2.3% and 2.2% effective primarily on August 1, 2021 and 2020, respectively.
The Asset-Based segment manages costs with shipment levels; however, increased shipment levels, freight profile changes, challenges with hiring an adequate number of personnel, and equipment capacity constraints pressured the efficiency of dock, street, and yard tasks during the three and nine months ended September 30, 2021. Shipments per DSY hour declined 2.4% and 0.7% for the three and nine months ended September 30, 2021, respectively, compared to the same periods of 2020, primarily due to inefficiencies driven by personnel and equipment capacity constraints related to the business growth and the effect of handling a higher number of larger LTL-rated shipments, including an increase in pieces per shipment. While the Asset-Based segment has added employees to service the business growth, the segment had to supplement resources with increased utilization of higher-cost purchased transportation in certain locations to manage service levels. The decrease in pounds per mile of 4.4% for each of the three- and nine-month periods ended September 30, 2021, respectively, compared to the same periods of 2020, was due to the higher number of miles (including purchased transportation miles) incurred to service the business growth and the increase in average length of haul resulting from intended changes in business mix, which was compensated by an increase in billed revenue per shipment.
Fuel, supplies, and expenses as a percentage of revenue increased 0.9 percentage points during the third quarter of 2021, and were consistent for the nine months ended September 30, 2021, compared to the same periods of 2020. Fuel, supplies, and expenses increased $16.8 million and $35.4 million for the three and nine months ended September 30, 2021, respectively, compared to the same prior-year period, primarily due to higher fuel costs as the Asset-Based segment’s average fuel price per gallon (excluding taxes) increased approximately 76% and 51% during the three and nine months ended September 30, 2021, respectively, compared to the same periods of 2020. More miles driven as a result of the increase in business levels also contributed to the year-over-year increases in fuel, supplies, and expenses. For the nine months ended September 30, 2021, fuel, supplies, and expenses was also impacted by higher expenses associated with increased business levels.
Depreciation and amortization as a percentage of revenue decreased 0.9 percentage points for each of the three- and nine-month periods ended September 30, 2021, compared to the same periods of 2020; however, depreciation and amortization expense was relatively consistent across the periods. The decrease in depreciation and amortization as a percentage of revenue was influenced by the effect of higher revenues, as a portion of operating costs are fixed in nature and decrease as a percent of revenue with increases in revenue levels.
Rents and purchased transportation as a percentage of revenue increased 1.7 and 2.9 percentage points for the three and nine months ended September 30, 2021, respectively, compared to the same periods of 2020, primarily due to higher utilization of rail, local delivery agents, and linehaul purchased transportation necessary to serve the needs of our customers as freight demand increased across the Asset-Based system during 2021. The year-over-year increases in purchased transportation costs were also impacted by higher fuel surcharges related to these services due to higher fuel costs. For the three- and nine-month periods ended September 30, 2021, rail miles increased approximately 10% and 28%, respectively, compared to the same prior-year periods.
Asset-Based Segment — October 2021
The year-over-year improvements in our Asset-Based business levels during the first nine months of 2021 continued during October 2021 as the segment benefited from a strong pricing environment and increased customer business levels. Although statistics for October 2021 have not been finalized, preliminary Asset-Based billed revenues increased approximately 20% on a per-day basis in October 2021, compared to October 2020, reflecting an increase in total billed revenue per hundredweight, including fuel surcharges, of approximately 18% and an increase in average daily total tonnage of approximately 1%. Total shipments per day increased approximately 1% in October 2021, compared to October 2020. Total weight per shipment remained flat in October 2021 versus the same prior-year period.
In recent years, excluding 2020, the historical average sequential change in our Asset-Based segment’s operating ratio in the fourth quarter, versus the third quarter, has been an increase of approximately 200 basis points. Current economic conditions and the Asset-Based segment’s pricing approach (which is described in the Asset-Based Segment Overview within the Results of Operations section of Item 7 (MD&A) of Part II of our 2020 Annual Report on Form 10-K) will continue to impact our Asset-Based segment’s tonnage levels and the prices it receives for its services and, as such, there