Although Bitcoin’s plunge yesterday surprised traders, market sentiment analysis showed that negative sentiment on Bitcoin has been going on for some time. The TIE data shows that Bitcoin's daily sentiment index has been declining in September. The index measures the amount of positive or negative talk about Bitcoin on Twitter. After hitting a high of about 80 earlier this month, the index turned negative a few days before the launch of Bakkt. At the time of writing, the index has fallen to 22.8, the lowest level since the collapse of the encryption market in November last year.