Why do the prices of 90% of the alt coins almost exactly follow BTC?

[beamin]

If you have coin base pro it lists the 15 or so most popular coins with little graphs and +/- in a list. The whole list with the exception of one coin will all be in the green or the red, and the price charts are very close to each other. What links them all together? Especially if a coin is etherium based another BTC and another based on some other coin. The stock market does this kind of but not to the T like BTC and Alts.

[mk4]

Alts mostly(obviously not 100% of the time) follow BTC simply because a significant percentage of these coins' and tokens' trading volume is against BTC (e.g. LTC/BTC, LINK/BTC, etc). That, and combining the fact that Bitcoin is the dominant cryptocurrency overall(the 60%+ BTC dominance metric is inaccurate and should be far higher).

[kolesozw]

If you have coin base pro it lists the 15 or so most popular coins with little graphs and +/- in a list. The whole list with the exception of one coin will all be in the green or the red, and the price charts are very close to each other. What links them all together? Especially if a coin is etherium based another BTC and another based on some other coin. The stock market does this kind of but not to the T like BTC and Alts.

Because the main trade markets of the alts are Bitcoin or other cryptos like Ether, so when Bitcoin loses a dollar value, the alts are following and vice versa.

If you check the alts Bitcoin price, you will notice that it's much more stable than the USD value.

[odolvlobo]

I think there are two reasons:

1. People trade all the different coins for the same reasons. So, any reasons for buying or selling bitcoin would also be reasons for buying or selling other coins.

2. Nearly all trading pairs include BTC, and the relative price wont change much without information that distinguishes between the two.

[Wexnident]

Simply speaking, the value of Bitcoin is tied to the value of altcoin. The domination of Bitcoin over the crypto market is quite obvious to be seen, and most often than not, altcoins are paired with Bitcoin most of the time so traders would buy altcoin then buy Bitcoin, which shows a symbiotic relationship between the two. There's also the idea of Bitcoin being the leading coin, add that together with altcoins being measured/paired with BTC, and you'd get what we have right now.

[fiulpro]

If you have coin base pro it lists the 15 or so most popular coins with little graphs and +/- in a list. The whole list with the exception of one coin will all be in the green or the red, and the price charts are very close to each other. What links them all together? Especially if a coin is etherium based another BTC and another based on some other coin. The stock market does this kind of but not to the T like BTC and Alts.

That is because of :

Trading
Not only that, many of the alts can't be purchased just like that , they are supposed to be traded against BTC which means that people will have to rely on bitcoins for them.
The transaction fee of these alts is also low which does mean that keeping them and transferring the money in them would be beneficial.

So when the price rises :
People does not only buy these alts to trade at the right time but as a whole the crypto community gets active and these lesser active alts gets a little boost from the people

Another reason !!
Much like ETH some of them also have a mutualistic relationship with BTC .
Which means instead of competition there is healthy support!

At the same time the more bitcoins rise in price , the more media coverage the crypto market gets now people tend to believe that they have lost the bull therefore they try and find other options to secure a good wallet in the future.

[amishmanish]

Questions like these mean we still have new people coming in. The price action is interesting to the traders always trying to find a correlation.

For the newbies, you should look for what they call the Alt-season. The Alt-season is when BTC has had its pump and interest gets renewed in crypto. This brings people into looking for alternates and a buying spree of Alts ensues. This is the time when most of the money is made in this market. We are in the Alt-season for the time being. The cycle will now keeps repeating albeit with lower amplitudes.

For anyone following these seasons, you have to know that when it does go down, every thing goes down. All the fiat goes back to fiat and all the ALT/ BTC goes back to BTC. So if you are actually trading, it is always the best decision to earn back your principal and leave most in BTC. Don't dabble too much into Alts as they can go to -90% within hours.

[Altcoinsintel]

Most altcoins are having the major trading volume in btc trading pairs, not in USD. In the case Bitcoin is rising but the altcoins aren't having traders selling them for BTC then  the price in satoshi value remains the same, thus they also increase in USD together with Bitcoin. This is how most altcoins are pegged in BTC terms. Usually they are traded and if Bitcoin escapes a major resistance level you will notice Bitcoin rising and altcoins staying behind, because traders move from altcoins to Bitcoin. But later they will get pumped again by the same whale traders and reach higher prices.

Lately Bitcoin dominance is moving between 60-70% for almost one year. Traders buy Bitcoin and sell their alts at 60% and do the opposite at 70%. If you look carefully at the market you will notice that. Bitcoin used to be 80-90% dominant in the market before 2017. This explains the altcoin mini seasons we see. 70% is probably the maximum BTC could get right now, so after that it is altcoins that are pumped by whales, with the help of the shill army in social media.

[GreatArkansas]

This illustration may be helpful. There are times that altcoins may dump if Bitcoin is pumping, just like what happened few days ago.
Also, looking at the Bitcoin Dominance also possible to identify altcoin price actions. Bitcoin dominance is measured by the market cap of Bitcoin and entire other cryptocurrencies.
What happened lately was increase in Bitcoin dominance and Bitcoin is pumping too.