Market cap BTC Dominance (BTC.D): is a very amazing to understand and predict Bitcoin and Altcoins trends.
BTC Dominance (BTC.D) is the total market cap of all the Cryptocurrencies compared against Bitcoin.
How BTC Dominance (BTC.D) work: when Bitcoin Dominance price is increasing, the price of Altcoins will be decreasing.
when Bitcoin Dominance price is decreasing, the price of Altcoins will be increasing.
For example:
BTC Dominance(BTC.D)
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Bitcoin (BTC)
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When you Look at both chart above, you will notice that from February till April when BTC was pumping, BTC Dominance was going down, and May till July when Bitcoin when and formed the descending channel, BTC Dominance was formed an arising wedge.
When BTC Dominance broke out of the arising wedge to the down side, that was when Bitcoin pumped from $29k to $50k and Altcoins pumped alongside with Bitcoin.
And on the 7th September, when the market experienced the huge dump, Bitcoin Dominance spiked up in price from $40.60 to $43.66. basically when BTC Dominance is increases, BTC and Altcoins prices will start decreasing. So you can use it as an extra tool to confirm your analysis and the current market trend.