Garbage in Garbage out
Garbage in Garbage out
Feb 1, 2011
This happens from time to time. I like to share it with you when it’s obvious on the web, so you can see it for yourself. The simple fact is that market data is not as precise as we’d like it to be.
Market data is our lifeblood. We examine every bit in so much detail. And we know it’s important to you, too. So we always try to get it right. But sometimes, the data just isn’t consistent. Sometimes, different sources will give you different answers to what you thought was a simple question. Yesterday, 1/31/2011, the question was, what’s the opening price for VIT?
Take a quick look. That’s quite an interesting stock chart. That’s the sort of thing that a lot of our customers are interested in.
Just one problem. When the day started we said the open price was $34.25. Later we changed that number to $32.44. If you use our change from the open filter 
https://trade-ideas.54solutions.com/Help.html#WSF_MinFOP that would make a significant difference. Why did we change it? The details are technical, but obviously it came from the market data. Obviously it came from what people reported to the exchanges, and what the exchanges passed on to us.
So, what’s the right answer? That depends on who you ask. Look at this list of daily prices that I got from Google.
It clearly says $34.25. Now look at the 5 minute chart from Google. Notice that I was hovering my mouse over the first 5 minute candle from 1/31. (Notice the blue circle on that candle, at the opening price.) So the prices near the top of the chart correspond to that candle. So the opening price for the first candle was $33.48. How can the open for the first candle of the day be different than the open for the day? Clearly there were data problems. At least three different answers seem reasonable for the opening price for that stock.
We know how important the data is for your trading. We always do our best to get this right. But, at the end of the day, you can’t expect perfection. We can’t give you better data than the exchanges give us. As you trade, please understand that market data is just the best approximation that’s available, nothing more.