Before we begin, I'd like to remind everyone that during the course of this conference, both in our prepared remarks and in answers to your questions, we may make statements related to future performance. Our statements represent our most reasonable estimates. However, since these estimates deal with future events, they are subject to numerous risks, uncertainties, and other factors that may cause the actual performance of American Water to be materially different from the performance indicated or implied by such statements. These risk factors are set forth in the Company's SEC filings which are available to the public in the company’s investment relations website.
With that I would now like to turn the call over to Jeff Sterba, our President and CEO.
Thanks Ed. Good morning all and thanks for joining us this morning. In addition to Ed, I have also got with me Ellen Wolf our Chief Financial Officer and Walter Lynch, President of the Regulated Operations. It's great to speak with all of you as we announce very strong quarterly results and our most recent consistent string of record setting quarterly earnings reports. Underlying the performance for the quarter is frankly one thing, consistent execution of our strategy. From investing appropriate capital to manage supply and delivery issues and that’s particularly given though weather challenges and drought conditions that we are facing throughout the country.
To drive operational expertise through developing a culture of continuous improvement and to growing our market based opportunities within and outside of our footprint is really execution that counts. All the while keeping the essential regulated feel of our cash flows our risk profile that you would expect when investing in the water utility sector while providing multiple avenues for solid growth.
So to summarize the quarter on slide five, you can see we have delivered very strong second quarter and year-to-date results and 11.5% increase in revenue quarter-over-quarter was coupled with solid cost control that resulted in an operating efficiency ratio for the last 12 months of 41.7% compared to 45.2% for the prior 12 months.