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The key word in your question is “significantly.” MAC address filtering does improve network security slightly, but it’s a pain to set up and the benefit is so marginal that I would not recommend it.
To be fair, an average joe just poking around trying to get free internet might be further discouraged if you have enabled MAC filtering. However, anyone who is seriously trying to hack your WiFi is going to be using a wireless network analyzer, which will show all of the MAC addresses on your network anyway. Then they can just change the MAC address of their computer to match one of yours, and Bob’s your uncle.