Welltower® delivers the health care infrastructure necessary to facilitate better treatment at lower costs and keep patients out of the hospital. Our business is centered on a relationship-based investing platform. We provide real estate capital to leading seniors housing operators, post-acute care providers and health systems. Through our capital, these companies are able to grow, innovate and ultimately provide better care.
Welltower is a $30-ish billion equity market cap publicly traded REIT that invest primarily in seniors housing, post acute care facilities and medical office buildings. We currently own 1,334 premier senior housing and long-term post acute assets across the U.S., UK and Canada, as well as 20 month 1 million square feet of self-managed medical office space in the U.S.
Before getting to the three reasons I just -- why investors should buy Welltower now. I wanted to highlight a few key things about our organization since we were last here in March of 2018; we delivered 15.3% total return to shareholders, outperforming all peers for the year; we completed over $4 billion of gross investment activity at a 7% yield, while selling nearly 2 billion of non-core assets, further improving the quality of our portfolio and cash flow; we leverage relationships with next-generation operators like Conseil to realign legacy relationships like Brookdale, enhancing the quality of our cash flow while positioning the Welltower platform for future growth; we experienced year-over-year occupancy gains during the fourth quarter for the first time since 2015, and we're encouraged by the general stabilization in seniors housing fundamentals seen during the second half of '18.
The portfolio has undergone a bit of a strategic shift over the past few years, adding significantly to its concentration of senior housing and outpatient medical facilities. In all, 63% of Welltower's income comes from senior housing and 27% comes from outpatient medical and health-system properties. In addition, 95% of the portfolio is private pay, which generally translates to more stable revenue than government-dependent payments such as Medicare and Medicaid.
o Reported net income attributable to common stockholders of $0.71 per diluted share and normalized FFO attributable to common stockholders of $1.02 per diluted share compared to $0.99 per diluted share in 2018, representing 3% normalized FFO growth o Total portfolio SSNOI grew 3.1%, driven by Seniors Housing Operating SSNOI growth of 3.0% o Completed $259 million of pro rata acquisitions in high quality real estate with an additional $519 million in pro rata acquisitions subsequent to quarter end for a total blended yield of 5.9% across eight separate transactions o Improved net debt to Adjusted EBITDA to 5.47x at March 31, 2019 from 5.84x at December 31, 2018 o Generated $538 million of gross proceeds from common stock issuances at an average price of $74.69 per share
On March 31, 2019, we had $249 million of cash and cash equivalents and $2.6 billion of available borrowing capacity under the unsecured revolving credit facility. During the first quarter, we generated approximately $538 million under our dividend reinvestment program and equity shelf program at an average price of $74.69 per share.
The Board of Directors declared a cash dividend for the quarter ended March 31, 2019 of $0.87 per share. On May 28, 2019, we will pay our 192^nd consecutive quarterly cash dividend to stockholders of record on May 14, 2019.