Ladies and gentlemen, welcome to the 2021 Annual Meeting of Stockholders of Highwoods Properties. This is Carlos Evans, Chairman of the company's Board of Directors. It's my honor to provide over this virtual stockholder meeting. The meeting will now come to order. The other participants in today's meeting are Ted Klink, our President and Chief Executive Officer and Jeff Miller, our Executive Vice President, General Counsel and Secretary.
Before we start with the business aspect of the meeting, I would like to welcome the rest of our Board members, all of whom are joining us virtually today. Chuck Anderson, who joined our Board in 2014. Chuck serves on the Investment Committee. Gene Anderson, who joined our Board in 1997, Gene serves on the Executive and Investment Committees. Tom Anderson, who joined our Board in 2020.
Tom serves on the Compensation and Governance Committee. David Gaddis, who joined our Board just this past January and serves on the Audit Committee. This will be David's 1st annual meeting. And on behalf of the rest of the Board, David, welcome to Highwoods. Dave Hartsell, who joined our Board in 2,009.
Dave serves on the Audit and Investment Committees. Sherry Kellett, who joined our Board in 2005. Sherry serves on the Audit Committee and Anne Lloyd. And last but not least, Anne, who joined our Board in 2018, Anne chairs our Audit Committee and also serves on the Executive Committee and Compensation and Governance Committee. We're also pleased to virtually welcome Doug Baker, representing Deloitte Contour, our independent auditor.
After the formal meeting has been adjourned, Ted will give a brief update about our company and then we will provide time for stockholders to ask general questions of management, the Board and Deloitte too. Only validated stockholders will be able to ask questions in the designated field on the web portal. Please note that this meeting is being recorded. However, no one attending via the webcast or telephone is permitted to use any audio recording device. Jeff, are we ready to proceed with the business portion of the meeting?
Yes, Carlos, we are ready. The record date for this meeting was March 9, 2021. There were 104,000,000,000,648 shares of common stock outstanding on the record date. Each share entitles the holder to one vote at this meeting. The holders of the majority of these shares are present in person or by proxy.
Based on Jeff's report, I can confirm that a quorum is in attendance at the meeting. As described in the annual meeting notice that was sent to shareholders in April, the purposes of this meeting are to 1, elect 9 directors for a 1 year term 2, ratify the appointment of Deloitte and Touche as our independent auditor for 2021 3, vote on an advisory proposal regarding executive compensation and to act on a proposal to approve our 2021 long term equity incentive plan. The polls are now open. Any stockholder who hasn't yet voted or wishes to change their vote may do so by clicking on the voting button on the web portal and following the instructions there. Stockholders who have sent in proxies or voted via telephone or Internet and do not want to change their vote do not need to take any further action.
Now that everyone has had the opportunity to vote, I now declare the polls for 2021 Howitz Properties Annual Stockholder Meeting Closed. Jeff, are you ready to report on the voting?
Has been approved by advisory vote and the 2021 long term equity incentive plan has been approved. The complete record of the vote will be filed as part of the minutes of this meeting and will be described in a Form 8 ks that will be filed with the SEC after the meeting.
With no further business, I now declare the business portion of this meeting adjourned. I will now turn the meeting over to Jeff to review a cautionary statement regarding forward looking information and then to Ted, who will provide a brief review of 2020 and the Q1 of 2021 and then review the COVID-nineteen pandemic's impact on the economy and on our businesses.
Thanks, Carlos. Forward looking statements made during Ted's presentation are subject to risks and uncertainties, which are discussed at length in our SEC filings. As you know, actual events and results can differ materially from these forward looking statements, and the company does not undertake a duty to update any forward looking statements. One of the most significant factors that could cause actual outcomes to differ materially from our forward looking statements is the ongoing adverse effect of the COVID-nineteen pandemic on our financial condition, operating results and cash flows, our customers, the real estate market in which we operate, the global economy and the financial markets. The extent to which the pandemic impacts us and our customers will depend on future developments, which are highly uncertain and cannot be predicted with confidence, including the scope, severity and duration of the pandemic and its ongoing impact on the U.
S. Economy and potential changes in customer behavior among others. With that, I'll now turn the call over to Ted.
Thank you, Jeff, and thanks to everyone for joining us on the call today for our 2021 Annual Shareholder Meeting. Let me start by saying that while 2020 was a unique, unexpected and challenging year for everyone, Highwoods weathered the COVID storm well, which I believe illustrates the resilience of our portfolio, our customers, our balance sheet and our team. I want to remind everybody that Highwoods has long been guided by a strategic plan and that plan will continue to guide the company. Our simple strategy is to own and manage high quality workplaces in the best business districts or BVDs within our footprint, maintain a strong balance sheet in order to be opportunistic throughout economic cycles, employ a talented and dedicated team to communicate transparently with all stakeholders. We focus on owning and managing buildings in the most dynamic and vibrant BVDs.
BVDs are highly energized and amenitized workplace locations that enhance our customers' ability to attract and retain talent. They are both urban and suburban. Providing the most talent supportive workplace options in these environments is core to what we call the Highwoods Workplace Making Strategy. Over the trailing 12 months, Highwoods has generated total return of 28%, outperforming both the average of our peers and all office REITs as a group. More importantly, we have outperformed the NAREIT office group over both 10 20 year time periods.
At year end 2020, our 25,900,000 square foot portfolio was 90.3% leased. Our average in place rents have grown at a compound annual growth rate of 4% since 2013. Importantly, over 80% of our pro form a revenues come from cities that have recently been designated among Urban Land Institute's top rated real estate markets for 2021. In 2020, we delivered FFO of $3.58 per share. While our performance was impacted by the economic disruption caused by the pandemic, we were able to deliver per share FFO excluding one time charges in line with our original expectations at the beginning of 2020.
We also generated positive NOI growth and GAAP rent growth during 2020. At the beginning of 2020, we also raised our dividend by 1.1% to $1.92 per share. This represents a 13% increase over the prior 4 years. I want to briefly review how Highwoods has been responding since the onset of the COVID-nineteen crisis in March of 2020. Our business continuity plan has remained in effect.
All of our buildings remained open and operating throughout the pandemic. We delivered return to work protocols for both our employees and buildings that are consistent with CDC and local government guidelines. And it is nice to finally see that some of our customers are starting to return to the office, albeit slowly. Importantly, we have collected more than 99% of our rents since the start of the pandemic. Early in the pandemic, during the height of business shutdowns and social distancing protocols, we worked closely with customers who demonstrated a legitimate need for rent relief.
We worked on mutually beneficial solutions and when appropriate, we did agree to defer but not abate rents for certain customers. And those repayments are being made on schedule. To date, we have been repaid more than 70% of deferred rents with a majority scheduled to be repaid by year end 2021. Plus, reduced capital expenditures has led to even stronger cash flows. Now turning to 2021.
As part of our first quarter earnings release 2 weeks ago, we updated our per share FFO outlook to $3.54 to $3.66 per share, implying a $0.02 increase at the midpoint from our original outlook of $3.50 to $3.66 per share. It's important to note however, the update excludes the impact of our planned acquisition of a portfolio of assets from preferred apartment communities and the subsequent sale of a portfolio of non core assets to fund the acquisition. We will update our 2021 outlook once the recently announced acquisition closes, which is anticipated to occur in the Q3 of this year. Our balance sheet remains in excellent shape. Our net debt to adjusted EBITDA was 5.1 times at the end of the first quarter.
We also recently recast our revolving line of credit and increased our borrowing capacity from $600,000,000 to $750,000,000 We reduced the borrowing spread by 10 basis points and extended the maturity date out to 2025, not including 2 6 month extension options. As of now, we have over $600,000,000 of remaining capacity on our revolver and only $66,000,000 dollars left to fund on our $394,000,000 development pipeline. We have no debt maturities until November 2022. We have long emphasized the importance of having significant customer, geographic and industry diversification across our portfolio. No market accounts for more than 21% of revenues, no customer other than the federal government accounts for more than 4% and no industry category accounts for more than 25%.
This diversification is serving us well in this uncertain macroeconomic environment. We've also worked hard to reduce our future lease expirations. We currently have the lowest cumulative 3 year lease expirations in over 20 years. And we have no expirations greater than 100,000 square feet remaining in 2021 or 2022. Our development continues to be a driver of growth for Highwoods.
Construction work on all of our development projects remained on budget and on schedule throughout the pandemic. In the Q1 of this year, we placed in service 2 100 percent leased developments and have a combined value of $108,000,000 and encompass 345,000 square feet. Our remaining pipeline is now $394,000,000 and is 75% pre leased. In addition, we have a land bank that can support $2,200,000,000 in future development, mostly in Nashville, Raleigh and Tampa. Last month, we announced an agreement to acquire a portfolio of office assets from preferred apartment communities.
The core portfolio to be acquired consists of 4 Class A office assets in Charlotte and Raleigh and 1 mixed use of redevelopment site in Atlanta. We also agreed to acquire 2 non core assets, a mezzanine loan related to a recently constructed office building in Atlanta and Armor Yards, a multi building creative office project in Atlanta. The estimated total investment, including the estimated value of the non core assets, is expected to be 769,000,000 dollars which includes $28,000,000 of near term billing improvements and $5,000,000 of transaction costs. We have posted $50,000,000 of non refundable earnest money deposits. And as I mentioned earlier, the transaction is expected to close in the Q3.
Four core office buildings in Charlotte and Raleigh, which encompass 1,600,000 square feet in total, were 95% leased at December 31, 2020 and had rent collections of over 99% during 2020. This high quality portfolio gives us entry into 2 new BBDs that have long been on our wish list, nearly doubles our presence in Charlotte to 1,600,000 square feet and further strengthens our market share in Raleigh. Further, there is long term upside from potential synergies with our existing portfolio and an attractive redevelopment parcel in Atlanta. Our plan is to effectively match fund our purchase by selling $500,000,000 to $600,000,000 of non core assets by mid-twenty 22. Importantly, once completed, we expect the portfolio rotation will be accretive to cash flow, roughly leverage neutral and neutral to our FFO run rate, while improving the quality of our portfolio and providing higher growth over time.
We remain highly committed to ESG. For example, during 2020, our greenhouse gas emissions were 26% lower than our 2016 base year. We also advanced our diversity and inclusion initiative with the overall goal of creating opportunities for all people in the commercial real estate industry, in the local communities in which we operate and within our own workforce. We're also proud of our diversity of our independent board members who have joined us for this meeting and half of whom are female or persons of color. We invite you to read more about our ESG commitment in our 2020 corporate responsibility report that was published last week and can be found on our website.
I'm very excited about the future of Highwoods. We have limited lease rollover risk over the next few years, built in growth from delivery of our development pipeline, recovering momentum in our markets and improving activity of our own leasing pipeline. And we're excited to once again deploy our proven playbook of opportunistically using our balance sheet for attractive investments such as the planned acquisition of a desirable and resilient portfolio of office assets from preferred apartment communities and then subsequently selling non core assets with less upside to return our balance sheet to pre acquisition metrics to reload our dry powder. In summary, we're confident we have the ingredients in place to drive sustainable growth over the long term. Now before I open
it up for questions,
I would like to thank our Board, our senior management team and our 360 coworkers for your continued hard work and dedication to Highwoods. I would also like to thank our shareholders for your continued interest in Highwoods. We remain focused on delivering strong results for you. I'll now open it up for questions.
Thank you, Ted. And as Ted has already said, we do want to open things up for stockholder questions that are entered today on the web portal. Please note that we will attempt to answer as many questions as time allows, but only questions that are germane to the meeting will be addressed. Ted, there are no questions?
Okay. Well, thank you again everybody for joining us on the call and thank you for your interest in Highwoods.
And before we conclude, I'd like to just say a few words. First of all, I'd like to applaud management, our directors and all of our employees for their tremendous efforts during the past year of unprecedented times. The Board and I shared Ted's view that with our fortress balance sheet, high quality portfolio and an incredible group of employees, we believe we are the best in the business and are well positioned to continue navigating COVID-nineteen and to capitalize on opportunities moving forward. I also thank each of you for your attendance, your interest in the company and for all of our stockholders and their continued belief and support of Highwoods Properties. The meeting is adjourned.