Long-term holders, who have held their Bitcoin for more than 12 months, are reluctant to spend their coins, according to Glassnode’s “The Week On-Chain” report. Another positive is that investors continue to withdraw coins from centralized exchanges whose share of supply has dropped to a new record low at 12.9%.
Long term relationships also strengthen, to some extent, around areas indicated as bubbles. The previously observed long term relationship between Google Trends and Bitcoin price [8] can also be seen here, between late 2012 and 2014 (period band 64–256). With the benefit of extra data it can be observed that the relationship disappears around 2014 (for lower period bands) and 2015 (for higher period bands), before the relationships start occurring more consistently in 2016 and 2017 (a region with a number of bubbles identified). The previously observed relationship between Wikipedia views and Bitcoin observed in 2013 (64–128 band), disappears before again returning in mid-2016 and 2017.

This is a stable coin, so it is pretty unique among other cryptocurrencies. Stable coins have the backing of fiat currencies such as the Euro or US dollar. This means that if an investor buys 1 Tether coin, they will have the same value of 1 fiat currency (backing the coin). Theoretically, what this means is that Tether will have a more stable value than other cryptocurrencies that suffer market volatility.
The SADF test finds the largest ADF statistic from all the windows considered. If this value exceeds a critical value, the null hypothesis can be rejected, and it is deemed the series displays explosive behaviour in at least one of the windows (taken as indication of a bubble occurring).