Updated about page.
This web script reads current and historical prices from Bitcoinaverage and presents the prices from some selected points in time.
There's a "semi-logarithmic" timescale of 3 day, 1 week, 1 month (30 days), 6 months, and 1 year. In addition, price from 1 Jan of the current year, this year's high, and this year's low are included.
I've also included the current (Sep 2014) record high price from Nov 2013.
In the data files from Bitcoinaverage, historical days have average, high, and low volume-weighted prices. The prices in the tables are average for each day, except of the highs and lows mentioned above.
The percentage in the table is
percentage = ( current_price - historical_price ) / historical_price * 100
This means that the current price is calculated using the formula
current_price = historical_price * (1 + percentage/100)
The number of coins at a certain date is calculated using extrapolated values from this page and multiplied with the price.
Note that this is a naive definition of "market cap" and not really applicable to Bitcoin, as it's not a share in a company. However it's widely used as a sort of benchmark within the community.
It's often postulated that Bitcoin's underlying price development is exponential (or rather, that it's in the "exponential" phase of a S-shaped saturation curve). To compare this, I calculated a best-fit line approximation against the natural log of the the average historical price, and this calculated price is presented compared to the actual prices.
I've also compared to a linear approximation, using the same methodology but of course using the straight numbers.
I've excluded all data newer than 3 days. The coefficients are updated daily. The values are shown in the headers.
I've used Julian dates to deal with the days, mostly because SQLite has built-in support for the datatype.
A received truth is that "no-one has ever lost money holding Bitcoin for one calendar year". We're a few months from testing that hypothesis. On the days leading up to 29 Nov 2014, the price rocketed from $130 to $1,100.
As there's often no direct average price that's the same as the current price, I've extrapolated the current price based on the slope of the price increase. I've then added 365 days to that extrapolated time and called that "red anniversary". If there's no new record high before 29 Nov 2014, a buyer of Bitcoin will be "in the red" after a year.
This line is based on averages since Nov 2013.
Q: why Perl? Why CGI? Are you some kind of Luddite?
A: Yes, it's what I'm most familiar with, and what's available on the server I'm using. I'm more interested in dealing with the actual data analysis, and I'm using tools I know about to deal with it.
Q: I love this page! Do you take Bitcoin donations?
A: I don't have a Bitcoin wallet, but I have a tip jar on Reddit. You can use that if you want. But I'd prefer if you'd donate to a charity instead. I don't need the money.
Questions? Comments? I'm gerikson on Twitter and Reddit.