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Excellent post, Richard.
BTW, I've had to take down my own basic version of the Yahoo data
downloader, mainly for reasons of inaccuracy and intermittent data.
My view remains that if the markets are more than just a hobby for
traders, quality (paid) data is essential.
jose '-)
--- In Metastockusers@xxxxxxxxxxxxxxx, "Richard Dale" <richard@xxxx>
wrote:
> There are plenty of quality issues with software that downloads from
Yahoo
> including:
>
> 1. Significant inaccuracies for any stock exchange that trades in
> increments less than 1c. This includes the Australian Stock
Exchange (ASX),
> Singapore Exchange, some NASDAQ stocks and most OTCBB & Pink Sheet
stocks.
> This happens because Yahoo's data is rounded to the nearest cent.
For
> example, there are 14000 listed instruments on the ASX. Over 8000
of them
> are currently trading below 20c which means they move in either 0.5
or 0.1c
> increments. Since Yahoo only prices in cents this introduce VERY
> SIGNIFICANT innacuracies. - eg. a 2.6c shown as 3c represents a 15%
error).
>
>
> 2. Normal dividends are adjusted by subtracting all historical
data by
> the dividend amount. Exchanges such as the ASX do not adjust price
data for
> standard dividends. By diluting it the way they do, any technical
analysis
> or backtesting no longer shows a correct % return, nor does it show
a
> critical technical levels such as support and resistance.
>
> 3. No sector information - critical if you want to perform
sector-based
> analysis.
>
> 4. Significant number of missing stock splits and other capital
> adjustments.
>
> 5. No delisted history - any system testing you do based on Yahoo
data is
> subject to population bias. ie you can only test on the stocks that
are
> currently listed.
>
> 6. There is no guarantee that Yahoo will continue to supply data,
> especially to automated download programs. In Yahoo's Terms of
Service,
> they have a clause which says "You agree not to reproduce,
duplicate, copy,
> sell, trade, resell or exploit for any commercial purposes, any
portion of
> the Service (including your Yahoo! I.D.), use of the Service, or
access to
> the Service.". Companies that produce Yahoo downloaders are
effectively
> exploiting the Yahoo service and are therefore in breach of the
Yahoo Terms
> of Service and Yahoo may shut down these types of automated Yahoo
> downloading programs very easily.
>
> So, whilst the Yahoo data is free to obtain from the Yahoo site, you
need to
> determine what you really need from the data. If you're every
likely to
> want to view historical charts (eg for system development /
backtesting /
> historical interest) then the old adage "you get what you pay for"
certainly
> applies here.
>
> The best analogy I can use for data feeds is they are like a game of
Chinese
> Whispers. <http://www.chinesewhispers.com/chinesewhispers.php>
> http://www.chinesewhispers.com/chinesewhispers.php
>
> In the case of programs that extract data from Yahoo, the exchange
sends
> data to Reuters. Reuters interpret the data, put it into their
databases,
> then take an extract of the data and send it to Yahoo. Yahoo
interprets the
> data, puts it into their database, then extracts it onto the Yahoo
Finance
> web site. Then the downloading program obtains data from the Yahoo
site,
> interprets it, and puts it onto the user's PC. If at any step of
the above
> process, the interpretation is slightly incorrect then you have a
> discrepancy between actual events on the market and data you
receive. This
> is clearly the case with Yahoo downloader products out there.
>
> Anyway, please understand what you are receiving with these products
and
> assess whether these issues affect your trading system development,
analysis
> or interpretation.
>
> Best regards,
> Richard Dale.
> Norgate Investor Services
> - Premium quality Stock, Futures and Foreign Exchange Data for
> markets in Australia, Asia, Canada, Europe, UK & USA -
> <http://www.premiumdata.net/> www.premiumdata.net
>
> _____
>
> From: MJ Jossart [mailto:mj008867@x...]
> Sent: Friday, 6 August 2004 7:36 PM
> To: Metastockusers@xxxxxxxxxxxxxxx
> Subject: Re: [Metastockusers] I Search a speed downloader for Yahoo
> historical !
>
>
> I asked the same kind of question in the EquisMetastock Yahaoo
group. I
> guess this would no problem if the Equis Downloader can support
multiple
> configurations, ... is it so ?
>
> ----- Original Message -----
>
> From: David <mailto:dhlinton@x...> Linton
> To: Metastockusers@xxxxxxxxxxxxxxx
> Sent: Thursday, August 05, 2004 11:08 PM
> Subject: Re: [Metastockusers] I Search a speed downloader for Yahoo
> historical !
>
>
> Would I have problems continuing with the Reuters feed for stocks
(to ensure
> data accuracy, splits, new symbols, etc) but using the Hyper Trader
Smart
> Downloader for free Yahoo indices and futures data?
> Thanks for your advice.
> David
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