Table: greg pursley
Question: What is the average difference between Greg Pursley's average start position and his average finish position across the years 1999 to 2010?
Step 1 (Operation, Filter): year
Step 2 (Operation, Indexing): avg start
Step 3 (Reasoning, Arithmetic): -, difference
Step 4 (Reasoning, Aggregating): AVG, average difference
Answer: 3.68