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wd,
Thanks for the heads up about certain aspects of CSI's data
as it deals with breadth, etc. I have filed your post in my
CSI notes so that if I consider developing a breadth
system, I will know what to watch out for.
WHY CSI DATA IS ESSENTIAL FOR ME:
My preference for CSI stock data arises from items that are
essential to the type of system development I focus on.
CSI has actual as well as adjusted prices and because some
of my filters are price sensitive I need to know the actual
trading prices of stocks for back testing.
Secondly CSI has inactive as well as active stocks, and I
need these as well because my systems give biased back test
results if I only look at those stocks that have survived.
CSI's CLEAN AND UNCLEAN DATA:
That does not mean that CSI is perfect. From what I have
seen, they appear to try as hard as any other provider to
give accurate data. Your pile of pens attests to their
desire to correct any mistakes that come to their
attention. That pile of pens also attests to the fact that
there are mistakes.
As a CSI subscriber I have noticed that when I do a daily
update, CSI sends the previous day's data to me as well as
today's. To my mind this implies two very important things
- first, CSI has a passion to give users the best data
available AT THE TIME, and second, that there MAY BE
mistakes in the daily data when it is first delivered to
users.
The possibility that CSI's data for the current day may
have some mistakes that will not be corrected until
tomorrow (or even later) has implications for my back
testing and for my actual trading.
TRADING IMPLICATIONS:
I might get a buy signal for a stock based on bad data in
today's down load for that stock. I may then buy the stock
at tomorrow's open and then discover that there was no buy
signal when I down load tomorrow's data which includes
corrections for the previous day's data.
What to do? If I knew of a cleaner data provider I would
switch, but I do not. So what to do with a buy signal
knowing that the data might not be perfectly clean?
I build the possibility of being wrong into my money
management plan.
BACKTESTING IMPLICATION:
When I run back tests, I know that I am getting somewhat
artificial results since I am using "cleaner" data in
testing than I will have when I actually trade. I see no
solution for this, so I just take back test results with an
extra grain of salt.
Ideally, I would like CSI to provide clean data (which I
would use for profit and loss calculations) and "raw" or
uncleaned, never corrected data, which I would use for
signal generation. That way my back testing would be closer
to the conditions I have to operate on when actually
trading.
CONCLUSION:
CSI is not perfect. But, as far as I know, it is still
better than the alternatives "most of the time" for "most
things" for the type of trading and system development that
I do.
However, I am thankful for users who point out limitations
in CSI data (ie, the breadth problem noted by wd).
b
--- wd <wdjd@xxxxxxxx> wrote:
>
>
>
> > Maybe - BUT how will you know which signals are valid?
> Oh yeah - you'll
> > know after they fix it (if they do) and your signal
> disappears or your
> trade
> > tanks and you spend countless hours trying to figure
> out why only to
> > discover a bad quote. But its only money, eh?
>
> I use quite a bit of breadth data in my system. I was a
> QP user for about 4
> years. Before then I used TC2k, AIQ and a host others. I
> did lose money one
> time (that I know of) because of bad breadth data when I
> was using QP. I
> complained several times on the QP list and other members
> checked into my
> complaints and found them valid. QP beat around the bush
> for several months
> while this was going on and I switched to CSI (I was told
> later by another
> member that QP did finally clean up their breadth data).
>
> I switched to CSI because of their reputation for clean
> data. I found most
> of their data to be clean (so far as I could tell), but I
> did find quite a
> bit of bad data in their breadth and indices. Not just
> minor indices, but
> even the SPX.
> CSI offers a CSI pen if you make them aware of any
> discrepancies. I have a
> desk full of them.
>
> I now use a paid data service for my breadth and indices
> that is far cheaper
> then the above two and I get my stocks/ funds from the
> various free data
> sources. I rarely have data issues with the free sources
> and when I do, I
> check with a couple of the other free data sources. This
> may happen one or
> twice a year.
>
> I am NOT saying this is the way to go for anyone, but it
> is most definitely
> for me. I don't have *full* confidence in my present data
> sources, but I do
> have more confidence in them then I do with some of the
> paid sources.
>
> Jim
>
>
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