Our variable cost, nonasset based business model continues to be an important advantage in all market environments. Our people managed our business efficiently in 2007, generating 22.0 percent growth in our operating income, to $509 million for the year. Our fully diluted earnings per share also exceeded our longterm growth target with an increase of 21.6 percent to $1.86 per share. We believe our decentralized structure, empowered employees, technology, and performance based compensation enable our people to be more productive than ever. Our variable incentive plans, including our equity awards which reward growth in profitability, do a great job of balancing employee and shareholder rewards.
We also believe that our size relative to the North American truckload marketplace is becoming an increasingly important competitive advantage. Our contract carrier base represents over one million pieces of equipment, and we manage approximately 25,000 shipments per business day. The larger we become, the more options we have for serving our customers. This enables us to reduce inefficiencies in the marketplace and provide better service.
As an integral part of our longterm perspective, we continue to maintain a strong balance sheet and financial position. At the end of 2007 we had approximately $455 million in cash and shortterm investments, with no longterm debt. While we understand the need to be responsible with any retained capital, we believe that our cash position gives us important flexibility to manage the business, build relationships, and make strategic investments to continue to grow the company. As economic uncertainty continues and economic challenges cause others to have to scale back, we think we are in a great position to continue to invest in our people and our network with new offices and new technologies, to keep looking at acquisitions, to keep offering quick payment programs to our carriers, and to explore other opportunities that help us grow and reinforce our commitments to be successful in all markets.