There's not necessarily any more current flowing in the ground trace, but yes, we want to reduce it's resistance/impedance so that currents flowing in it don't create much voltage drop. Ideally, the ground/reference voltage trace voltages should be the same at every point on the trace.Oops!
What this means??: "any potential difference is the 'noise'".
What I seem to understand from your posts is that we make ground trace wider because
more current is following through it and so we try to choice a wider trace for the ground to have less RESISTANCE in the ground trace,right?
I guess you won't need an explanation paper about wider supply traces. Take a look at the attached sample PCB and decide what all other ICs will do if relay K1 pulls in.I think I need an explanation paper about the philosophy of wide trace for ground and for metallic objects in a circuit (like a metallic covered inductor inside a radio).