Two ways to make the label mean something — and to leave data out of the fit
percentage prints the slope × 100. That is only a meaningful
percentage when the y values are fractions of a whole and x is a real unit: here
the share of households adopting a service goes from 5 % to 13 % over eight years,
and the label reads 1.15 % per year.
percentage off there{x, y} points, so one x step is one year, not one data point
The last two quarters jump away from the series. trendoffset: -2 excludes
them from the fit — and, because the line runs from the first to the last included
point, it visibly stops before them.
trendoffset: 2 starts at the thirdtrendoffset: -2 stops two from the end{x, y} objects — this chart uses numbers