Netflix made headlines in September 2011 when it split its streaming video service and its DVD by-mail service into two companies. This decision was based on projections that streaming videos will replace DVDs in the future. In this problem, you will explore these projections. Numbers below are close to the correct values, but vary to allow more practice with this idea. 

Total DVD and Blu-ray disc sales in 2009 were $8.72 billion. For the purposes of this problem, you will combine DVD and Blue-ray disk sales into one category of DVD sales. A study by In-Stat predicted that "physical disc sales will decline by $4.7 billion by 2014," and that "streaming, on the other hand, should grow from its current $2.1 billion to $6.3 billion over the same time period (2009–2014)."

Write a statement interpreting the meaning of the slope in the context of the problem.