Im confused too why this things happen

, if I remember last year when BTC pump altcoin dumps and when BTC dump altcoin pump , but right now there are moving in the same trend if BTC dump altcoin dump much more

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This question bothers me too. What i have noticed is when the price of bitcoin goes up , the price of altcoin goes down and when the price of bitcoin goes down the price of altcoin goes up. So i think its invesely proportional to the price of bitcoin. But sometimes the prices go oppposite. So there is no fixed equation to the proportionality of their prices.
This is actually the hardest thing on trading crypto market which you wont really know if they are complete correlated or not since they do really change their trend to each other.They do go opposite, they go the same directions anytime they do move which would really make the things more harder for us who do make trades. Im not really so sure too what are the things that do makes this thing happen.