Differences in public data

M

marsman

Ok, people have told me not to use public data sources like yahoo and google. Yes, they are right.

FYI here are again gigantic differences between yahoo and google.
Google seems to degrade each day more and more: just take a look at the differences:

HTZ_google.png


HTZ_yahoo.png
 
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general comment:
When posting something like this, it is helpful to provide a clue to what is giving you concern, if you really expect feedback. AKA what specific difference do you observe, and why does it give you concern?
Note: the last prices are identical!
 
stepandfetchit said:
general comment:
When posting something like this, it is helpful to provide a clue to what is giving you concern, if you really expect feedback. AKA what specific difference do you observe, and why does it give you concern?
Note: the last prices are identical!
More...
For example what is the reason behind such big differences in the volumes? I mean the many strikes with missing volumes on the google page.
Volume is an important indicator for activity and liquidity (for that strike)...
 
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K. I see that now! I just pulled up TOS and get a different set of numbers for option volume for that contract series. It is possible the data source for the different providers varies, so may be necessary to dig a little deeper for how the option volume for illiquid options such as those Hertz weeklies are derived (do they collect the volume from all or only some exchanges?). Since I am only trading SPX and RUT options that are a lot more liquid, this has not been an issue for me. (if the volume is approximately correct, I don't currently have issue) If the data does not support your requirement, you may need to find data that does. For example, the Google data you referenced implies no trades occurred today on the Friday expiration of HTZ $8.00 Call strike, but Yahoo indicates 3 trades occurred. (TOS indicates NO trades occurred as well)!
Illiquid contracts will have a number of issues that keep most of us away from them.

upload_2016-6-22_17-40-4.png
 
It seems you have practically the same data like google. Then the question arises which of them is accurate, and wyh such diffences at all?
They should be the same, especially at EOD...
 
If you find useful information on accuracy of option volume, please post.
If we find data (option volume) varying broker to broker, it seems prudent to follow-up to find out why, so we understand why. Incorrect data (option volume) from free services such as Yahoo and Google, would not surprise me and using that to make decisions may not be wise.
 
Options trade on multiple exchanges - one might be reporting just a single exchange (eg CBOE), others a couple of exchanges, and others the "Tape" - i.e. all trades reported from all venues including ECNs.

Certain trade condition codes might contribute to volume on one platform and not on another.

You'll only know if you get a comprehensive Time & Sales report for "the tape" and work through it.
 
FYI: The option volume reported by TOS in the Option Chains seems to inaccurate.
I have a position as shown in the clip below, which indicates Volume is zero.
upload_2016-6-24_8-1-30.png

However, the Chart for THAT option, indicates a 84 trades have occurred.
upload_2016-6-24_8-4-14.png


Interesting!!!
 
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