After the first test, the grades were averaged, and everyone got a B. The students who studied hard were upset, and the students who studied little were happy. But as the second test rolled around, the students who studied little had studied even less, and the ones who studied hard decided they wanted a free ride too; so they studied little. The second test average was a D. No one was happy.
When the third test rolled around, the average was an F. The scores never increased as bickering, blame, name-calling all resulted in hard feelings, and no one would study for the benefit of anyone else. All failed to their great surprise, and the professor told them that Socialism would also ultimately fail because when the reward is great, the effort to succeed is great, but when government takes all the reward away, no one will try or want to succeed.
Could not be any simpler than that.... tho there are still some that say: "Ours will be different."