We fostered enduring tenant relationships through a service-oriented culture and maintain a solid balance sheet, which Christina will speak to, which is more important than ever to attract and renew quality tenants as they consider to making long-term lease commitments. The average occupancy in our multifamily portfolio was 98.1% in the fourth quarter and continues to benefit from strong market fundamentals that validates our prior investments into these assets. So once again, we had a solid fourth quarter that completed a very good year in 2023. We signed over 950,000 square feet of commercial leases and increased our Manhattan office portfolio lease percentage by 250 basis points from a year ago to 92.1% at year-end, which represents a 510 basis point increase since the end of 2021.
We are well positioned to lease space and achieve positive lease absorption again in 2024 with modest lease expirations for the year and a healthy pipeline of new leases to start the year. And we continue to see impressive performance in our multifamily portfolio. Thank you. And before I turn the call over to Christina, I want to extend my congratulations to both Christina and Steve on your well-deserved promotions. Having worked closely alongside both of you these past few years, I have immense confidence in your abilities and the value you bring to ESRT. I’m also optimistic that our ongoing partnership will yield fresh opportunities and enhanced value for ESRT shareholders. Christina?
Christina Chiu: Thanks, Tom. For the fourth quarter of 2023, we reported core FFO of $68 million or $0.25 per diluted share, which increased 15% year-over-year. This was largely driven by strong same-store property cash NOI growth, strong performance from our Observatory business as well as higher interest income year-over-year. Results for the quarter included approximately $0.015 of nonrecurring items, mostly within other income. Same-store property cash NOI increased 11.3% year-over-year primarily driven by higher revenues from early cash rent commencement, free rent burn-off, higher tenant expense reimbursements and higher other income. These revenue items came in ahead of expectations embedded in our same-store property cash NOI guidance for the year.
The higher revenues in the fourth quarter were partially offset by an increase in property operating expenses which we anticipated in our guidance, albeit the increase was less than what we expected due to a few successful tax appeals that resulted in refunds as well as some repair and maintenance cost savings relative to expectations. Overall, as mentioned, there were approximately $4 million or $0.015 of nonrecurring items that benefited same-store NOI in the fourth quarter. In the fourth quarter, the Observatory generated net operating income of $27 million, an increase of 13% year-over-year. Revenue per capita remains high and admissions continued to improve year-over-year. Observatory expense was $9.3 million in the fourth quarter. For the full-year 2023, the Observatory generated NOI of $94 million, and that exceeded the midpoint of our guidance for the year.
For the full-year, we reported core FFO of $0.93 per diluted share. Within fourth quarter results, each of the building blocks, same-store revenues, same-store expenses, Observatory NOI that we provided in our full-year guidance table happen to skew to the favorable side, which contributed to the large beat relative to our 2023 FFO guidance. As mentioned in the release, 2023 results also included approximately $0.03 of items that were nonrecurring in nature and also benefited from higher-than-expected interest income. As of December 31, 2023, the company had total liquidity of $1.2 billion, which was comprised of $347 million of cash and $850 million of undrawn capacity on our revolving credit facility. At quarter end, the company had net debt of $2.2 billion with a weighted average interest rate of 3.9% and a weighted average term to maturity of 5.4 years.
We have strong liquidity, no floating rate debt exposure, a well-laddered debt maturity schedule and the lowest leverage among all New York City focused REITs at 5.4x net debt-to-adjusted EBITDA. ESRT owns 100% of our commercial assets with no complex JV structures, and that allows for great opportunity and flexibility for future financing and capitalization. With this balance sheet flexibility, over the past two years, we actively recycled capital in a tax-efficient manner, pursued investment opportunities that are additive to our New York City focused portfolio and repurchased our shares. And we will continue to allocate capital to generate shareholder value. Now on to our outlook for 2024. We expect 2024 core FFO to range between $0.90 and $0.94 per diluted share, which compares to 2023 core FFO of $0.90 per share, excluding nonrecurring items.
Let me spend a moment to discuss the assumptions used in our guidance. In 2024, we expect same-store cash NOI to be modestly positive at the midpoint, with a range of down 1% to up 2% relative to 2023 levels. Within this range, we expect positive revenue growth, which assumes commercial occupancy of 87% to 89% by year-end 2024, up from 86.3% at year-end 2023, driven by a strong pipeline of signed leases not yet commenced and manageable lease expirations in 2024. On the expense side, we expect an approximate 6% to 8% increase in forecasted property operating expenses and real estate taxes in 2024, which is partially offset by higher tenant expense reimbursement income. It is important to note that 2023 operating expenses ultimately increased 6.8% from the prior year, about 120 basis points lighter than the 8% year-over-year growth anticipated in our 2023 guidance driven by tax refunds, some R&M cost savings and timing changes from certain projects that will now fall into 2024.
