Stable coins - Price, volume history and changes with bitcoin fluctuations

Stable coins have their impacts on crypto market. Usually, when more Tether USD is minted (from the air or from any asset used to back it, it is not an objective for this topic discussion), the crypto market has a big wave.

To start, I give you some documents to read:

In this thread, I will present 2 parts:

Part 1: The price and volume history of some stable coins.
Part 2: Changes of stable coin price with fluctuations (rises/ falls) of bitcoin
Data sources: https://coinmarketcap.com/

Part 1
In this thread, I collected data and analysis for stable coins as follow:

USDT
USDC
BUSD
DAI
TUSD
GUSD
PAX
EOSDT

The era of stable coins probably began in 2017 (this statement is based on the data, and I've not yet digged deeply to their histories).
Let's jump to their daily volumes and summary stats for the period from Jan 2020 to 8 Jan 2021. This step is to classify them into high and low daily volume categories.

USDT (Tether USD) is outperforms others in daily volume. You can see this fact with median (p50), minimum (min) and maximum (max) values.
The next two stable coins are: USDC and BUSD.
Hence, I will run analysis for 2 categories: High volume (USDT, BUSD, and USDC -- it is unfair for USDT to be classified in the same category with BUSD and USDC but let it be); and Low volume (DAI, TUSD, GUSD, PAX, and EOSDT)
In this analysis, I convert original figures from coinmarketcap.com to $billion

Raw result

Code:

    variable |         N      mean        sd       p50       p25       p75       min       max
-------------+--------------------------------------------------------------------------------
     USDTbil |     374.0      45.6      19.2      43.3      33.1      54.3      15.4     131.6
      DAIbil |     374.0       0.1       0.1       0.0       0.0       0.1       0.0       1.2
     TUSDbil |     374.0       0.3       0.3       0.1       0.1       0.5       0.0       1.8
     GUSDbil |     374.0       0.0       0.0       0.0       0.0       0.0       0.0       0.1
      PAXbil |     374.0       0.3       0.3       0.2       0.2       0.4       0.1       1.5
     USDCbil |     374.0       0.6       0.4       0.5       0.4       0.7       0.2       3.3
     BUSDbil |     374.0       0.3       0.5       0.1       0.1       0.4       0.0       3.4
    EOSDTbil |     374.0       0.0       0.0       0.0       0.0       0.0       0.0       0.0
----------------------------------------------------------------------------------------------

Box plots

I exclude USDT from box plots for other stable coins and run a special one for it, stratifying over months (from Jan 2020 to 8 Jan 2021).
With the box plot, you can with non-USDT stable coins, the best three ones are: USDC, PAX and BUSD. Best here means the highest vertical lines inside box plots for each stable coin. The line represents for median value.
If you notice in the raw result table, with the p75 value, BUSD and PAX have same value at 0.4 bil. that is almost half of USDC at 0.7 bil. I did not look deeper but I guess BUSD only grown well in later of 2020. I will run further analysis later for BUSD.
USDT: Its volume increases since Jan 2020, and remains almost stable from Feb 2020 to May 2020 before having drops within 2 months (Jun - July 2020). After that, it rises a lot till Jan 2021. The box plot reflects this fact very well.
Note: In all box plots, outliers are excluded to make it visual readable

Time series plots
In the plot for top 3 stable coins, I used the multiplier at 10 for BUSD and USDC to make plots more visually comparative.

Even with the multiplier, volume of BUSD and USDC are still very smaller than volume of USDT.
From these plots, you can see the business launch periods or at least the appearance on coinmarketcap of 3 stable coins: USDT (early of 2017), USDC (in late of second half of 2018), BUSD (in late of the second half of 2019)
Interesting point is both USDC and BUSD have later appearance dates on coinmarketcap than a few other stable coins. Impressively, they have been growing faster. It is not a surprise if you know they are backed by Binance and Coinbase.

Part 2 (will be updated later, but it will be something like that and maybe with some upgraded ideas)

Bitcoin pumps/ dumps and altcoin price actions (2013 - 2020)
See the section for stable coin in that thread
I've not yet include bitcoin price and its rises/ falls with +/-5% as the previous analysis

From the raw result table, the box plot (with width of boxes and ranges between whiskers), and the bar chart, I can draw some conclusions

Stable coins are not truly stable in their prices (as many people believe in or as those companies try to seed their products). What are stable coins if they indeed have changes more than 10 percent between 2 consecutive days.
It is the rates for global market and I expect for bigger % in local markets.
USDT is the best stable coin in stability (interquartile range from p25 to p75 values, min and max values)
The 2 worst stable coins in stability are EOSDT and PAX.

Raw results

Code:

    variable |         N      mean        sd       p50       p25       p75       min       max
-------------+--------------------------------------------------------------------------------
   pclowUSDT |     373.0       0.0       0.8       0.0      -0.1       0.1      -7.1      10.1
   pclowBUSD |     373.0       0.0       0.9       0.0      -0.1       0.1      -7.2      11.6
    pclowDAI |     373.0       0.0       1.0       0.0      -0.2       0.3      -5.9       5.3
  pclowEOSDT |     373.0       0.0       2.0      -0.0      -0.5       0.4     -18.3      25.3
   pclowGUSD |     373.0       0.0       1.5       0.0      -0.4       0.4     -12.2       7.4
    pclowPAX |     373.0       0.0       1.0       0.0      -0.1       0.2      -9.6      12.7
   pclowTUSD |     373.0       0.0       0.6       0.0      -0.1       0.1      -4.6       4.9
----------------------------------------------------------------------------------------------