Thank you, Jeff, and good morning, everyone. Please turn to Slide 12, where we'll discuss our Q1 2021 collections. Our hard-working associates have been committed to working closely with our neighbors throughout the pandemic. These efforts continue to pay off.
Our second quarter 2020 collections have increased to 93%, up from our originally announced figure of 86%. Our third quarter 2020 collections have increased to 96%, up from 94%, and our fourth quarter 2020 collections have increased to 96%, up from 95%. These positive results continued through the first quarter of 2021 as we collected 95% of rent and recoveries build, and this trend continues to improve.
Slide 13 reviews our year-to-date same-center NOI, or net operating income. We have been successful in mitigating the impact that the COVID-19 pandemic had on our portfolio but our results were impacted, nonetheless. Our first quarter 2021 same-center NOI decreased 0.9% to $86.5 million from a year ago.
Results were driven by a 0.8% decrease in average same-center occupancy and an increase in rent abatements as PECO works with certain neighbors in helping them recover from the negative impact of the COVID-19 pandemic. Partially offsetting this decrease was a $0.52 or 4.1% increase in the same center average base rent per square foot.
Please note that our same-center NOI includes 274 properties that we have owned and operated since January 1, 2020.
Slide 14 outlines our net income and core funds from operations, or core FFO, for the quarter ended March 31, 2021. Our core FFO increased 5.5% to $63.6 million. On a per share basis, core FFO increased by $0.02 to $0.20 per diluted share during the first quarter of 2021. The increase in core FFO for the first quarter of 2021 was driven by the consistent property earnings that I just spoke to, lower interest costs and decreased general and administrative expenses. Core FFO per share also benefited from fewer shares outstanding as a result of our tender offer, which closed in December 2020.
Slide 15 outlines our debt profile and maturity ladder as of March 31, 2021. Our net debt to adjusted EBITDA was 7.4x at March 31, 2021, compared to 7.3x at December 31, 2020. At March 31, 2021, our debt had a weighted average interest of 3% and a weighted average maturity of 3.8 years. Approximately 70% of our debt was fixed rate. This compares to December 31, 2020, when we had a weighted average interest rate of 3.1%, a weighted average maturity of 4.1 years and approximately 75% fixed rate debt. While we are comfortable with our leverage in the current environment, we would like to continue to improve this ratio over time.
Lastly, we have $490 million of borrowing capacity available on our $500 million revolving credit facility.
I would now like to turn the call back over to Jeff to discuss our historical performance. Jeff?