Quote from: Roy Badami on January 28, 2014, 08:41:56 PM

Quote from: BitcoinAverage on January 28, 2014, 03:33:44 PM

[We do not consider MtGox as "valid price source", as for me - none of the individual exchanges are. But as long as they are not faking their ticker figures and someone is still willing to trade there even considering fiat withdrawal problems - we should count it in as one of the market players.
Since MtGox volume is not decisive anymore even for USD market (not to mention global averages) - we don't see the need to exclude it. It exists and works, it is a part of the global landscape, whether we like it or not, and we have to include it.

Alex at BitcoinAverage.

Could I just check with you.... when computing Mt Gox's volume for a currency, do you make sure only to inlcude primary transactions as returned by the Mt Gox API? If not, you will end up, the global average will end up double counting transactions that are cross-matched between, e.g. the EUR and USD orderbooks (which Mt. Gox.'s multi-currency ordermatching will do if it's still the best order on the orderbook, taking into account the Gox currency conversion fee).

roy

Hmm, this is a good question actually. We're using their API tickers, which provide trading volumes separately for different currencies. I assume they do calculations right and not provide doubled volumes through their API, however I couldn't find this explicitly stated anywhere. I'll approach them directly and find out. Will update you when I'll know more.

Quote from: Roy Badami on January 28, 2014, 09:00:15 PM

Quote from: BitcoinAverage on January 27, 2014, 07:52:55 PM

Historical data - hmm, we're saving data daily, but it's not available online, only by request. I can get it for you if you need, just ask. It will be daily per-minute CSVs, but it's not going to long in the past, as we've started tracking global averages not so long ago.

Ah, that's way more detail than I want. Ok, let me take a step back and explain what I'm really looking for...

I would like to see a daily indicative Bitcoin price for each calendar day (ideally both published on the web site and accessible by an API). There is often a need to determine the market value of an asset for tax or accounting purposes. For pragmatic reasons, in many circumstances it is adequate to calculate the market value using an indicative price for the asset on the day in question; for shares, published daily closing prices are often used for this purpose.

Currently the only published indicative daily prices for Bitcoin are Coindesk's published 'closing prices' for their Bitcoin Price Index. I don't find their methodology ideal for a number of reasons, but that's a separate discussion. For now, what I'd like to see is more providers publishing such pricing data.

I don't have a strong feeling how the daily price index should be calculated. Volume-weighted average over the day? Midprice at a particular time of day? (Noon? End-of-day? i.e. midnight.) Nor do I have a strong feeling for what timezone is used to define 'day'.

It would be great to have more options for getting data like this than Coindesk's current data...

roy

Hmm, I see what you mean now.
I think "closing price" here would be not really fair, as any particular time you'll pick up for this calculation will be inevitably favoring some markets that fit their daytime trading activity nicely and neglect others.
A volume-weighted average over last 24h seems much better to me here. Because it will include activity on all global markets, which ranges and differs a lot during the day, and won't favor particular markets above the others, but will consider trading volume only, which is measurable and unbiased parameter. And it can be shot at any time during the day, particular time is not important in this case. Midnight by GMT would be handy reference point probably.

Alex at BitcoinAverage