<t>Another way (if you want a continuous change rather than discrete) you can take logartithms and then a time derivative (often used for, say, growth rates in an economy).Ex:Y(t)=gdp level at time 't'.log Y(t)then d log Y(t) /dt= (dY(t)/dt )/YdY(t)/dt is the time change, dividing it by Y (the whole...