Although year-to-date, export scrap volumes have stayed relatively flat versus 2011, the volatility from the month-to-month has been very significant. And export sales prices have also been quite volatile during the last nine months with a peak to trough difference of approximately $100, and with an overall trend downwards during this time period. Falling price environments typically act as a damper on supply flows, and our margins have compressed during this time period as purchase prices have not fallen as quickly as sales prices.
Notwithstanding these headwinds, we have been able to maintain our financial discipline by staying focused on the things that we can control. We remain highly focused on maintaining our positive cash metal spreads, extracting synergies between our MRB and APB divisions, reducing SG&A throughout the company, and strengthening our supply chain and our operating efficiencies. This has enabled us to generate strong operating cash flows and to execute a balanced capital allocation strategy. We have reduced our outstanding debt, we have returned capital to our shareholder through share purchases, we have substantially increased our annual dividend to $0.75 per share, and we have been able to continue to invest in the growth of our business.
Our capital allocation strategy is a reflection of the long-term strength of our business model. We have a uniquely positioned operating platform, which enables us to meet the fundamental demand that exists, and is expected to continue. The developing world is still growing and is still short of scrap. So let's turn to slide five to take a deeper dive into our sales and supply markets.