Thank you, Greg, and good morning. Old Dominion's revenue for the first quarter of 2021 was $1.1 billion, which was a 14.1% increase from the prior year despite having one less work day.
Our operating ratio improved 530 basis points to 76.1% and earnings per diluted share increase to $1.70.
Our per day revenue growth of 15.9% included a nice mix of increases in both our LTL tons and yield. LTL tons per day increased 10%, while our LTL revenue per hundredweight increased 5.6%.
We are winning market share as demand for our industry leading service has increased while the domestic economy is improving.
In addition to our service advantage that includes 99% on time performance and a cargo claims ratio of 0.1%, our proven strategy of investing and service center capacity ahead of anticipated growth has also provided us with a capacity advantage in the marketplace. This strategy is different for many of our competitors, as we believe the average number of service centers operated by the other large LTL carriers has decreased over the past 10 years. We currently have approximately 25% excess capacity within our service center network, which is in line with our long term targets and we plan to further expand our network this year to stay ahead of our growth.
Our plan is to ensure that our network is never a limiting factor to growth. On a sequential basis, revenue per day for the first quarter increase 3.3% as compared to the fourth quarter of 2020 with LTL tons per day increasing 0.7% and LTL shipments per day increasing 1.5%. These were all above our normal sequential trends, which typically declined from the fourth quarter. The monthly sequential changes in LTL tons per day during the first quarter were as follows; January increased 0.3% as compared with December, February decreased 4.4% versus January, and March increased 10.7% as compared to February. The 10-year average change for the respective months are an increase of 1.2% in January, an increase of 2.2% in February, and an increase of 5.1% in March.
While there are still many workdays that remain in April, our revenue performance has remained strong.
Our month to-date revenue per day has increased by approximately 45% to 50% when compared to April of 2020.
As a reminder, our revenue decreased 19.3% in April 2020, due to the significant impact of the COVID related shutdowns.
We will provide the actual revenue related details for April in our first quarter form 10-Q.
Our first quarter operating ratio improved to 76.1% with improvements in both our direct operating cost and overhead cost as a percent of revenue.
We have said many times before that the long term improvement or operating ratio requires an improvement in density and yield, both of which are generally supported by a favorable macro economic environment. The strength of our first quarter results reflect how important these factors are to our success.
Our direct costs benefited from an improvement in our line-haul laden-load average and pick up delivery shipments per hour during the quarter. We lost a little productivity on the dock. But that is common when business levels accelerate and we add a significant number of new employees.
While we would like to see our platform productivity improved, we believe it is more important for these employees to properly load our trailers to maximize employee safety in line-haul efficiency, while also protecting free from damage.
As Greg mentioned, we will continue to add drivers and platform employees during the second quarter as our volume trends continue to accelerate.
We will also continue to use purchase transportation to supplement our workforce until the capacity of our team can support our anticipated growth. We improved our overhead cost as a percent of revenue during the first quarter primarily by successfully leveraging a revenue growth.
As expected and mentioned on our fourth quarter call, certain calls that were reduced in 2020 because of the pandemic have started to increase.
While many of these calls such as travel and customer entertainment are not completely back to pre-pandemic levels.
We expect that there will be sequential increases in aggregate overhead costs this year.
We will maintain our disciplined approach to controlling discretionary spending however, and make every effort to minimize cost inflation and other areas. Old Dominion's cash flow from operations total $310.3 million for the first quarter and capital expenditures were $51 million. We currently anticipate our capital expenditures to be approximately $605 million this year, which includes $275 million for service center expansion projects. We utilize $309 million for our share repurchase program and paid $23.2 million in dividends during the first quarter. The total share repurchase amount includes $275 million attributable to an accelerated share repurchase agreement that was executed during the first quarter.
Our first quarter shares outstanding reflects the initial delivery of shares under this Agreement, and a final calculation of total shares. repurchased will occur no later than the end of August of this year.
Our effective tax rate for the first quarter of 2021 was 26.0% as compared to 26.3% in the first quarter of 2020. And we currently expect our annual effective tax rate to be 26.0% for the second quarter of 2021. This concludes our prepared remarks this morning. Operator, we would be happy to open the floor for questions at this time.