Why does Yahoo Finance and Google Finance not match historical prices?

Was working on a different question to ask on here, and realized I might be completely wrong when I realized the historical data on Yahoo and Google are completely different. Therefore I have no idea which is true.

And to confirm I understood Google right I went into their actual Historical price lookup:

Does anyone know which is correct? Are they using two different calculations?

• how do they handle splits? Jun 25, 2014 at 17:04
• @mhoran_psprep I really hope you're not asking me. I'm completely new to all this Jun 25, 2014 at 17:06
• And don't get me started on how for some securities there are gaps in the graph (literally missing lots of trading days in some cases) or the fact that you can't scroll back very far even though the slider makes it look like you should.
– user12515
Jun 26, 2014 at 17:29

The difference is that Yahoo is showing the unadjusted price that the security traded for on that date, while google is adjusting for price splits. This means that Google is showing how much you would have had to pay to get what is now one share. Since 1979, JNJ has split 3-for-1 once, and 2-for-1 four times. 3x2x2x2x2 = 48. If you bought 1 share at that time, you would now have 48 shares today. Yahoo is showing a price of \$66 for what was then 1 share. \$66/48 = 1.375, which Google rounds to 1.38. You can see this if you get the prices from May 14-21, 1981. The stock split 3-for-1, and the price dropped from 108 to 36.38.

Yahoo's adjusted close column has not been accurate since they re-wrote the Finance website. It now just represents the closing price.

The other relevant field on Yahoo is the Adj. Close. This adjusts for splits, but also adjusts for dividends. Hence why this doesn't match either the Google or Yahoo numbers.

I work on a buy-side firm, so I know how these small data issues can drive us crazy. Hope my answer below can help you:

Reason for price difference:

1. Vendor and data source

Basically, data providers such as Google and Yahoo redistribute EOD data by aggregating data from their vendors. Although the raw data is taken from the same exchanges, different vendors tend to collect them through different trading platforms. For example, Yahoo, is getting stock data from Hemscott (which was acquired by Morningstar), which is not the most accurate source of EOD stocks. Google gets data from Deutsche Börse.

To make the process more complicated, each vendor can choose to get EOD data from another EOD data provider or the exchange itself, or they can produce their own open, high, low, close and volume from the actual trade tick-data, and these data may come from any exchanges.

For equities data, the re-distributor usually adjusts the raw data by applying certain customized procedures. This includes adjustment for corporate actions, such as dividends and splits. For futures data, rolling is required, and back-ward and for-warding rolling can be chosen. Different adjustment methods can lead to different price display.