Lol, it's pikachu!
Falcon can't approach from above, but that goes for pretty much all the capn's matchups. Pika is fast but Falcon is faster. Uairs out of shield work against grabby Falcons who poke your shield. Watch the dashdance, it's means either nothing or that he's coming for you.
Don't up+b into the ledge unless you have to or if Falcon is not at the edge, go far behind Falcon otherwise. You will get spiked if Falcon is waiting there.
Offstage, Falcon gets hardcore gimped basically every time, whether by a pika fsmash at the ledge to stop a jump or an up+b (which even catches Falcons recovering from below the edge) or bairs and uairs far off the stage, where Falcon really has no options (Just don't jump into the Falcon punch plz). Even Down+B can catch a recovering Falcon.
Best edgeguarder in the game against one of the worst recoverers.
Pika can shave stocks off falcon super-quick this way and it's hard to be combo'd consistently by Falcon because Pika is light and has the up+b escape. Contrarywise, Falcon is heavy and can be juggled a lot by Pika's superior aerials.
If a Falcon is about to hit you offstage with a Bair, your aerials will trade hits but put you at huge disadvantage. Up+B will get you hit if the Falcon is already there.
So, if the Falcon is crazy enough to jump out at you, get back to the stage before him. Be wary of getting mindgamed - Falcon bair-ing to bait Pika's up+b might get you back and laggy onstage ready to be bthrowed.
I'm not sure about a specific number ratio. Obviously in pika's favour by a good deal.