I am wondering about the huge differences of the data provider google finance and yahoo finance. I am interested in the monthly data from adidas listed on xetra. In google: ETR:ADS and in yahoo finance: ADS.DE - Xetra.
There is a huge difference in the data, e.g. consider the 02.06.2008:
google finance:
Date Open High Low Close Volume
Jun 2, 2008 45.49 45.60 44.93 45.05 1,037,644
yahoo finance (german):
Datum Eröffnungskurs Max. Tief Schluss Ø Volumen Adj. Schluss*
2. Jun 2008 45,49 46,48 39,39 40,11 1.603.100 38,34
As you can see the open ("Eröffnungskurs") is the same. But all other values are different. So currency seems not to be the problem. But why are these values so different?
Also, why is there a yahoo finance gap in August 2008? I don't get the value of the 01.08.2008 but the 18. Aug 2008 instead? Since I am using the yahoo finance data I have to fill in this gap, what value / what method would be appropriate?
Answer
The difference is usually explained by
- the way the end-providers (Google, Yahoo) aggregate the data they get from their vendors
- getting prices from same exchange, but from different trading platforms
- different adjustments and corrections during post trading period
- missing corporate actions or dividends and many more.
If you have a discrepancy in a price usually it's a good practice to check Investor Relations section on company's website. For example, for Adidas you'd see that the correct value for 6/2/2008 is 45.05.
The ultimate source, of course, would be checking the exchange for that price. If exchange allows to get the price that far back one should use that value. Frankfurt Stock Exchange in this case allows you to get this period. Note that there are two tabs: Xetra and Frankfurt, they simply represent two different trading platforms.
Yahoo, btw, is getting stock data from Hemscott (which was acquired by Mornignstar.) Hemscott is not the most accurate source of EOD stocks. Google is getting the data from SIX Financial (former Telekurs).
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