In real world, can a multiplier be equal to 10 or even 20?

Question

Does a multiplier effect play a major role in determining the effectiveness of the policy?

Answer 1

Not really. It is usually around 1.14

Answer 2

Yes, the multiplier can be very high at 10 or 29 in poor countries with no big wealthy people. The people consume nearly as much as their income; mpc = 0.9 or 0.95

Yes the multiplier effect can play a major role in determing the effectiveness of economic policy, especially in lifting economies quicker from the recessions and depressions.