I am about to apply traditional univariate GARCH tools to analyze the volatility of the Bitcoin - US Dollar exchange rate.
The index that I would like to investigate is the Bitcoin Market Price (hereafter simply "BMP") that is compiled and reported by the Blockchain.info information provider at this link: https://blockchain.info/en/charts/market-price.
Blockchain.info provides open, high, low, close and 24h-average exchange rates series. In my analysis, I will use the 24h-average series.
The above page's headline states that the BMP is an "average USD market price across major bitcoin exchanges" which, I guess, are those tracked at the "Markets" section of the website.
PS: I do not have at least 10 points of reputation right now. Therefore, I cannot post here the link for the Markets page which is one of the top-screen ribbons on the main page of the website.
So, my question is:
Is there any available detailed information on how the BMP is technically calculated?
It would be of particular interest to me to know the following:
a) Is the BMP calculated as an average of the exchange rates that are tracked at the Markets section that I already mentioned? If so, what kind of average? (e.g. simple, weighed, etc.)
b) Is the BMP weighed by the four exchanges' respective transaction volumes?
c) Are Bitcoin trades other than those with US Dollar included in the BMP? If so, which (official/unofficial) fiat exchange rates are used to state the BMP in US Dollar terms?
d) How often is the BMP updated during any calendar day? Does update take place every 15 minutes (i.e. time for the Blockchain.info Price API to update) ?
Basically, what I am looking for is a schedule of the criteria for the calculation of the BMP like the one that e.g. Coindesk provides for its own ticker.
I hope the question is clear enough.
Any help is deeply appreciated.