Today, Extra Space Storage continues to be at the forefront of the self-storage industry. Over the past 12 quarters, we have led the sector in average same-store performance. We have become the second-largest self-storage operator in the industry because of the quality of our properties, the efficiency of our operations and the experience of our team.
Last year we increased our same-store revenue by 2.3% and net operating income (NOI) by 3.4%, including tenant reinsurance revenue. Though not as high as in previous years, our same-store performance was impressive given tough comparables and a decelerating operating environment.
Houston was one of our best performing markets in the aftermath of Hurricane Ike, and other top performing markets for the year included Chicago, Dallas, Denver, Oakland and San Francisco. The strength of those markets was partially offset by weakness in Florida, Las Vegas, Philadelphia and Phoenix.
Our revenue management team continues to implement pricing strategies utilizing information gained from over a dozen different pricing tests on 75,000 customers. Our street rents, or incoming rents, are competitive in the market, and we continue to offer discounts to attract new customers. We have improved retention by pulling back on certain existing customer rate increases as needed on a property-by-property basis.
Our marketing strategies continue to evolve as more prospective customers utilize the Internet as their primary tool for choosing a self-storage provider. In late 2008, Extra Space Storage was one of four companies that won Google’s “Website Workout” contest, which gave us access to online consultants to help us optimize paid and organic searches using Google's analytical tools. We believe the knowledge gained by this collaboration will help us further refine our Web marketing strategies and have a positive impact on conversion rates and rentals.
In 2008, we continued our ongoing commitment to improve our portfolio through strategic acquisitions and development while at the same time investing in our existing portfolio. We acquired 11 high quality properties for $79.9 million, and completed the development of nine self-storage properties located in core markets such as California, Florida, Illinois and New Jersey for approximately $77.1 million. We invested $12.4 million to improve our existing properties, making them even more attractive to new customers and showing our commitment to the “Clean and Green” standard.
