NYSE Cumulative Advance-Decline Line

[gekko71]

Hi All,

Why does the Weekly NYSE Cumulative Advance-Decline Line based on $ADD look so much different than the one provided by StockCharts.com and FreeStockCharts.com?

Thanks

G.

[gekko71]

The daily cumulative is consistent (a straightforward summation). It's the weekly or the monthly which are totally different. The timeframe used shouldn't affect the calculation, or should it?

Does anyone have any idea?

Thanks

G.

[gekko71]

Anyone from eSignal able to cast some light on this? Any idea welcome.

Thanks in advance

G.

[ScottJ]

Stats like $ADV and $DECL are snapshots (usually at 6 second intervals) and represent the # of NYSE issues that are up or down at that moment, respectively. $ADD is simply the difference between the two.

I looked at stockcharts.com but have no idea how they are calculating $NYAD, for ex.

Thanks.

[gekko71]

I think the problem is that on a weekly chart you're only taking the last read of the week - that is Friday - totally disregarding the days in between. This is bound to skew the cumulative total.

So I don't think they use a fancy formula, they just see weeks as made up of 5 days (or less depending on holidays and stuff).

Unfortunately I don't think I could fix the problem just by tweeking the EFS since you really need to know how many days during a particular week the exchange was open.

The only way - in my opinion - to solve the problem would be for eSignal to provide the Cumulative stats.


G.

[ScottJ]

Originally posted by gekko71
I think the problem is that on a weekly chart you're only taking the last read of the week - that is Friday - totally disregarding the days in between. This is bound to skew the cumulative total.

G.

That's actually not the case. If you look at the weekly data, you'll see we are capturing the open (Monday), close (Fri) and whatever the high and low EOD values were during the week. Again, these are snapshot figures and not meant to be "cumulative".

Thanks.

[gekko71]

Of course they are 'snapshot' figures, how else would you determine the number of advancing and declining issues at any one time if not by taking a 'snapshot'? If you string together lots of 'snapshots' then you end up with a cumulative total (which is a running sum).

The daily total is correct since you only need to work out the Advances and the Declines at the end of the day. Add 'em all up and you have a nice AD Line consistent with all the other AD lines out there.

For the week and the month though things are a little more complicated since you can't just take one snapshot at the beginning of the week and one at the end of the week. You need to add up every single day between Mon and Fri.

Like I said, it should be done at the source.

Thanks

G.

[ScottJ]

I just looked at freestockcharts.com and stockcharts.com and comparing $NYAD on both of those with $ADD on our system, the weekly and monthly charts appear to be in sync pattern wise. Some providers may opt to make the # cumulative but we elect not to do that and it would appear those two other sites handle the same way.

btw, in terms of slight fluctuations in the actual #'s, those are usually attributed to timing and whether preferreds, class stocks, etc are included or excluded.

Thanks.

[gekko71]

Thanks for the quick reply