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Finance sites erroneously show Amazon, Apple, other stocks crashing

marketwatch.com

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Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#31

Post by tunetine »

cbanek wrote: post #7

I've actually seen a number of times where Google Finance has a daily low that was never reached or a high that wasn't shown on the graph (sometimes many percentage points away). It's also notoriously bad when there's a gap up or down, and will sometimes cut out various parts of the graph. But still, seems to be one of the better ones out there, as I still use it. Just don't treat it as authority. Another interesting…

If I had to guess, it looks like google and yahoo track by time. Each nth second it plots a point, so it's likely to miss graphing the actual high or low of the day.

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#32

Post by vpribish »

This was a market half-day: exercising some code-paths that haven't been used since the day after thanksgiving '16. I do find it surprising that google and yahoo are both affected, as they used to have very different patterns of stock data errors (yahoo was much higher quality).

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#33

Post by tybit »

ams6110 wrote: post #26
Flammy wrote: post #6

Earlier quoted context omitted.

Stock tracking websites don't need to be perfect, just need to be better than the humans they replaced. Faster, free, and less errors doesn't mean they must be error free. Self driving cars just need to be better than humans, and given the number of teens and senior citizens on the road...

As someone contemplating the purchase of one, a self-driving car needs to be better than me . That's a higher bar than better than average even if it's not objectively correct.

On the other hand, as a passenger on public transport, taxis and ride shares it only has to be better than (often over worked and over tired) average human drivers.

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#34

Post by vpribish »

pishpash wrote: post #21
cbanek wrote: post #7

I've actually seen a number of times where Google Finance has a daily low that was never reached or a high that wasn't shown on the graph (sometimes many percentage points away). It's also notoriously bad when there's a gap up or down, and will sometimes cut out various parts of the graph. But still, seems to be one of the better ones out there, as I still use it. Just don't treat it as authority. Another interesting…

Google Finance does not even have a working price plotter, that's pretty awful in a basic way.

and their financial news is flooded to uselessness with bot-written "stories" from sites like "The [register|tribune|bulletin|news|alert]". The service is pretty garbage now.

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#35

Post by vpribish »

kwelstr wrote: post #2

Wow, that's crazy! What algorithm did this, or maybe it's some scheme manipulation for profit? You can never be sure when something like this happens, flash stock crashes have a history that's muddy at best. :/

your paranoia level is set a titch high - this is incompetence, not malice.

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#37

Post by cbanek »

tunetine wrote: post #31
cbanek wrote: post #7

I've actually seen a number of times where Google Finance has a daily low that was never reached or a high that wasn't shown on the graph (sometimes many percentage points away). It's also notoriously bad when there's a gap up or down, and will sometimes cut out various parts of the graph. But still, seems to be one of the better ones out there, as I still use it. Just don't treat it as authority. Another interesting…

If I had to guess, it looks like google and yahoo track by time. Each nth second it plots a point, so it's likely to miss graphing the actual high or low of the day.

I thought this too, but looked at the daily high and daily low at Fidelity, and it matched the actual low on both the graphs (which were the same). I figure it's either some data blip, or maybe some kind of dark pool trading that was logged after hours.

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#38

Post by trothamel »

One nice thing about SEC-regulated markets - unlike the various cryptocurrency markets - is that it's possible for trades to be rolled back if they are "clearly erroneous". That isn't perfect - if the data is only a little off, it might not be possible to get a trade rolled back - but it tends to limit how much havoc is called.

https://www.sec.gov/news/press/2009/2009-215.htm

(My understanding is that trades can also be rolled back in the case of security breaches, at least at the exchange and broker levels.)

Re: Finance sites erroneously show Amazon, Apple, other stocks crashing

#40

Post by simonsarris »

ams6110 wrote: post #3

And we trust that software can drive our cars for us?

We are all running software to drive our cars. Sometimes the software gets drunk, or has a stroke or a diabetic fit or just drops hot coffee all over the hardware.
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