I've been trying to build a trading algorithm and fooled myself into thinking it worked. Turns out, Google Finance quite often returns the wrong data. Not "sorry, we couldn't return data for this stock" - but factually incorrect closing prices for each day.
Just look at how for weeks at a time Google thinks the price remained the same, when theydidn't.
Can someone confirm the data is actually incorrect and there isn't a great explanation behind why the prices being displayed are what they are? Additionally if you have suggestions in mind about how to recognise stocks with bad data so they can be ignored or a better API for that matter, it'd help a lot!