In the book there are sophisticated (but easy to follow) formulas and frameworks to work out this impact in real terms (such as an equivalent number of cars on the road).
Yn y llyfr mae fformiwlâu a fframweithiau soffistigedig (ond hawdd eu dilyn) i ddeall yr effaith hon mewn termau real (megis y nifer gyfatebol o geir ar y ffordd).