You'd be surprised how much of a buff 10% can be. You also did incorrect math.   Base Rate: 1/30000 = ~0.00003333333 Current Donor Buff: 1/27000 = ~0.00003703703 Your Proposal: 1/21000 = ~0.00004761904   You may think that's a small change, but 10% in probabilities turns into a significant buff over a large period of time. There is one way to effectively increase your odds of finding a shiny and that is by farming hordes. I'll use a 5 Pokemon horde for this example.