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After USDT appearance on ERC20 and TRC20, the total USDT on ERC20 is dominated the total supply of Tether USD. It is easily understandable because of the fast transaction speed and cheap transaction fees (except lately skyrocket of fees on Ethereum network weeks ago).
Coin Metrics' State of the Network: Issue 56
Tuesday, June 23rd, 2020
Coin Metrics
Jun 23
Tether Supply Growth is Slowing
Since the beginning of the coronavirus-related lockdowns, Tether supply growth has been extremely strong. Here we show Tether’s free float supply, a measure of supply that represents the amount of supply freely available for purchase by investors. Notably, it excludes Tether that has been issued but not yet released. This year, a fairly steady rate of growth brought total Tether free float supply from around 5 billion units to 9 billion units. In just the past few weeks, however, Tether supply growth has slowed considerably, although it is still positive.

Source: Coin Metrics Network Data Pro
Although the assumption that Tether is fully backed by fiat currency is tenuous and not fully proven, one interpretation of Tether supply growth is that it represents new capital inflows into the space. The common narrative is that Tether is printed, sent to exchanges, and then used to purchase Bitcoin or other cryptoassets. Here we plot one-month Bitcoin price growth with one-month Tether supply growth to examine the connection. Recent data points to a tight correlation between the two time series. As Tether supply growth has slowed, Bitcoin’s price growth has also attenuated.