Polo and Coinmarketcap Differences

[shamzblueworld]

So I've noticed something today, there is quite a difference in 24h %Change at coinmarketcap and poloniex, for example for ZCash, at coinmarketcap its +9.81 whereas at polo its -1.67, hence there is also difference in their value.
I thought the values/price or changes of different crypto currencies are universal, clearly I am wrong.
Anyone care to elaborate please?

[Supercrypt]

The polinex exchange is like stock market, the value is decided upon how many people wants to buy xcoin and how many people wants to sell xcoin, now thanks to arbitrage there are a lot of exchanges close to price with each other and not a lot of difference in price for them, otherwise people would buy at one place and sell at other, however there are small differences, small enough to not make arbitrage worthwhile. That is why you may see differences between two places.

[shamzblueworld]

The polinex exchange is like stock market, the value is decided upon how many people wants to buy xcoin and how many people wants to sell xcoin, now thanks to arbitrage there are a lot of exchanges close to price with each other and not a lot of difference in price for them, otherwise people would buy at one place and sell at other, however there are small differences, small enough to not make arbitrage worthwhile. That is why you may see differences between two places.

Got it, thank you.
So in trading the overall price matters but more important is the place/exchange where you're trading, especially if its short term and for quick profit on pump/dump.
So I guess the number of people on an exchange or trading site will also matter because they are the ones deciding the value on the exchange.