# Describing growth on a finite scale

We are discussing this chart: http://i.stack.imgur.com/ecCRG.png

D in 2011 was -5.6 along x D in 2013 is -4.5 along x

D in 2013 is more right-wing than in 2011.

When describing 'how much more right-wing is D', is it correct to describe the change in the points relatively using a %?

Change towards right = 1-(-5.6/-4.5) = '20% more right wing'

Or because the scale is finite (-10 to 10) and D has moved along one point, is D '5% more right-wing'?

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There's a lot of arbitrariness in the scale. If it was $-10^\circ$ C yesterday and is $-8^\circ$ C today, is it $20\%$ warmer? I'd rather only specify the absolute difference – Hagen von Eitzen Feb 11 at 13:07