plot swathchart
    xlabels, swath, transparent very light red swath, blue line
  with
    comment ""
    comment "   Use swath to highlight a region"
    legend
    gridlines
select
  year, average * 0.80, average * 1.20 as 'Average +/- 20%', 
      average as 'Average'
  from CPI
  where  year > 1967 and year < 2007;