The market capitalisation of Bitcoin (BTC) has been in a marked downtrend versus other digital assets for most of 2020. In fact, the leading cryptocurrency actually lost market share to the rest of the industry for the last 11 days.Whilst not a record in terms of severity of the drops, it is in terms of duration. Some are interpreting the declining Bitcoin dominance as a sign of an impending altcoin rally.Is Alt Season Here? Bitcoin Dominance Continues to DropAs pointed out by the author of An Altcoin Trader’s Handbook, Nik Patel, BTC dominance has spent more than a week dropping consistently. In fact it has been in decline for all of February and much of January.Bitcoin has now lost dominance for 11 consecutive days. This has literally never happened before. The previous record for consecutive days of decreasing dominance was 9 days, occurring between 9th March 2017 – 17th March 2017.— Nik Patel (@cointradernik) February 11, 2020Bitcoin dominance was as high as 68.35 percent at the beginning of 2020. It has since slumped to just a 63.39 percent share of the wider crypto asset market.As Patel highlights above, Bitcoin has never lost dominance for as many consecutive days as it currently has. The previous period of such sustained falling market share was in March 2017. Bitcoin dominance fell consistently over a nine day period during the significant year.Spring 2017… Didn’t Something Important Happen Around then?Those who were around the cryptocurrency industry in early 2017 should realise that the previous record for falling Bitcoin dominance almost immediately preceded the bull market that saw Bitcoin rise to almost $20,000 and some altcoins having runs of 10,000 percent or more.The performances of XRP, NEM, DASH, XLM, and ETH, all dwarfed Bitcoin’s humble 1,000 percent gains that year. Of course, the subsequent bear market saw those coins with the biggest gains also lose the most. With BTC dominance once again rising in a similar fashion to that kicked off the mania of 2017, some observers are expecting an impending rerun of previous “alt seasons”. In response to Patel’s tweet above several respondents seemed optimistic that altcoins would continue to outperform BTC in the coming weeks.However, the two longest BTC dominance drops are not quite the same. Over the previous 11 days, Bitcoin’s market capitalisation has fallen by just under 3 percent.During the nine day period in March 2017, the decline of Bitcoin dominance was much more significant. Between March 9 and March 17 Bitcoin dominance fell from around 83 percent to just over 75 percent.In 2017, BTC dominance continued to fall until summer. The scaling debate reached its divisive end with the creation of Bitcoin Cash and optimism returned to the Bitcoin market.Fuelled by the successful addition of SegWit, Bitcoin would go on to take back dominance until its all-time high just short of $20,000. As the market topped, money flooded into altcoins once again, creating a second altseason during which many cryptocurrencies reached their current all-time highs.Time will tell if history will repeat in the coming weeks and months of this year. However, the industry seems increasingly bullish about the potential for another parabolic rise across all digital assets. Related Reading: White House Moves Towards Intense Crypto Crackdown, What Will it Mean for Investors?Featured Image from Shutterstock.