The combination of Bitcoin and Ethereum currently account for approximately 62% of $2.6 trillion total crypto market cap. This Number has been subject to some sizable fluctuations between 45% in 2018 to a high above 80% in march of 2021, The general trend however since early 2018 has been sideways to slightly higher.
Now, the market cap number are interesting, but alone they dont fully illustrate the market dominance of the big two coins.
The market cap difference between the big two and the next closest competitor has grown considerably from when ripple had almost 18% of the total market cap of 2017, to today where binance coins has 3.8% as the next closest competitor.
There is one more element to the story that suggests the Bitcoin and etherum dominance is strengthening. Since May 2021, the price correlation between the two has tightened significantly. To me this is a sign that the market is over convicted in the belief that there are the big two amd the rest of the crypto space. Now going forward traders will be closely watching not only the relationship between Bitcoin and Ethereum but also between those two and potential relevant competing coins.