About 60% of the people you meet will say he does not exist.
About 40% of the people you meet will say he does exist.
Now, those 60% of people clearly don't believe. Perhaps the crazy thought of his existence is too magical and make-believe, and to them, it is clear and quite obvious that such a man cannot exist. Or, as they grew up, their parents did not believe in Old Saint Nick and that doubt of his existence spread right down to those other 60% of people. Really, I think it's all about distribution of disbelief.
Now, for the 40%. All I can say is that people say "yes". And sometimes they have sightings and evidence to back it up. It's as simple as that.
But you may notice that the ratio is not 50/50. More people don't believe, and this number of those individuals grow each year. It's like the existence of God, or a god; now, no one believes in one as science has successfully proven other-wise.
Now, I will admit that the idea of Santa clause seems made-up or even childish. Even the fact that mathematically in order to reach all believer's homes he must enter 1,178 homes per second is a bit astonishing. But I'm not saying he is not real. Honestly, I am not sure if he truly does still exist or not. For me, there's a 75% chance that he does not exist, but there's still 25% percent left for the thought of accepting his existence. And I'm not going to stop believing until the non-real percentage reaches 100%, which I think will never happen.
I think that it is highly likely that this man DID exist long ago, and did use to give poor children presents. And this created the thought of Santa Claus. But does he still exist and do this today? How can he? As a child, do you think your parents would sneak out and buy you all of those presents even if they couldn't afford them? Well, only if they (or you) didn't believe. In many families, Santa brings gifts to the parents as well. It's just very rare as parents, having a mind that thinks logically, do not often believe in a man like this.
If someone says there is no Santa, he or she clearly does not believe. And what happens when you don't believe? He does not come to your house. There. A perfect set-up for someone to be sure that he does not exist. But if you don't believe, you will actually never know if he really does exist. If you do believe, he will come, but you may never have pure evidence that it actually was him, not your parents. But when you don't believe, your percentage of likely-hood of his existence immediately drops to a 0%, where if you do believe, it should be between a 100%-1%. Remember, you still believe until you reach a 0%.
So my advice to you is to really do what you want. If you want him to be real, believe. If you don't, don't believe. Ignore anyone who tells you what they believe, because what they say is not fact... it is opinion. As we get older, we tend to loose faith in his existence, and eventually our default answer to whether he exists or not will be "no". This is shown in any TV show or Movie that denies Santa Claus's existence. If you search Santa up on Wikipedia or in the Dictionary it will most likely denise his existence because both of those sources are logically driven. (By the way, children finding other's opinions in trustworthy sources like the internet or dictionary is one of the most common ways for a child to stop believing in Santa Claus).
The real answer of whether he exists or not will still be present, but I think we will never truly know it. No one will ever have 100% accurate evidence that he does not exist, but then again, it is rather unlikely that someone will be able to find 100% accurate evidence that he DOES exist. It's a tricky concept to wrap your mind around, but if you think about it for a while, it will all come back to the same answer: We will never know.
So, that is why I tell you to believe what you believe. Do what you think is right. I believe in Santa Claus, and guess what: he HAS come. There; proof from a believer. And how likely is it that a non-beleiever will believe the believer? Well, the non-believer can't see Santa for evidence, so the believer in this scenario would be a little stuck getting the non-believer do believe, don't you think? Unfortunately, that's how our life is working now. It's much easier to get people not to believe than to get them TO believe.
So, here's what's going to happen: If you don't believe, he won't come. If you do, well, we will see what happens. We will see what happens...