>
> How about "there could be
> alternative explanations for the observed correlation"?


Probably a more accurate statement than my previous one.


> Talks, cheap,
> Justin--how about offering some plausible explanatory "variables," along
> with supportive evidence?


I'm not certain I'm able to rival, challenge, or in any way compete with
some of the collective wisdom on this thread. But it would probably be a
good exercise for me to attempt it.

It appears you compiled the chart with the intention of looking at per hive
averages, and then comparing them to colony numbers. When you chart them
(which thank you for taking that time to do so) and you back up you see an
inverse relationship. But is that what's really happening?

Several of the reporting periods for numbers of hives have MASSIVE
reporting gaps. 10 years between the first and second, 12 years between the
second and the third, and another 10 years between the third and fourth
reporting periods. Its incredibly difficult to say that each one of those
data points is a true representative of the "average" number of hives for a
decades worth of time. For a given year, I'm sure its accurate. But for a
previous 5 and post 5? Tough to draw that conclusion. For example, if I
used 1968's "per hive" average as my only indication of the average for
that decade, I would have assumed it was roughly 40 lbs per hive, but if I
used 1969's average (a year later) I would have assumed it was roughly 60
lbs per hive, or a 50% higher number. Without looking at data on a yearly
basis before and after (or a more regular interval than a decade), you
can't tell which one is an outlier. So I think its very difficult to get
any long term average numbers from those data points, especially when you
are trying to indicate a trend.

Alternatively, the years of 1977-1982, 1986-1991, and 2008-2016 appear to
have fairly repeatable data points. And all three of those ranges appear to
have hive numbers that are somewhat consistent, i.e. not large changes.
During the same time periods, the "per hive" averages appear to also be
somewhat consistent (although with much more extreme highs and lows). So if
I take an average number of colonies for each of those three time periods,
and compare it to an per hive average during those time periods, I may be
able to glean some important information about trends. To me, everything
before 1977 and the 2000 data point are difficult to determine whether they
are outliers or not.

So what happened between 1982 and 1986 that could have changed both per
hive averages and colony numbers? Oddly enough, Acarapis woodi showed up
right in the middle. Perhaps a coincidence.
So what happened between 1991 and 2008 that could have changed both per
hive averages and colony numbers? Oddly enough, Varroa destructor took a
massive foothold, along with all of the associated viruses (while varroa
was introduced into the states in 1987, I don't think it was as wide spread
to affect most hives until the early 90's, but I wasn't keeping bees then,
so I'm going off reports of what others have told me). I could also point
to CCD here, but I'm not ready to open that can of worms.

The introduction of new parasites could easily explain the decrease in
colony numbers. The decrease in colony numbers as a result of new parasites
could also have removed from many commercial operations stocks or genetic
lines that produced less honey (on the basis that previously some of those
hives may have been "coached through" to make it, while post-parasite they
would perish on their own) thereby increasing the per hive average. The
introduction of new chemicals into hives to combat the parasites, as well
as changes in management practices, could also likely impact per hive
averages.

Of course, there are some large assumptions that need to be made to draw
those conclusions: namely the removal of 25% of the data points, or that
you are doing so not because they aren't accurate but instead because doing
so fits a hypothesis, thereby showing that if you torture the math enough
it will tell you anything.

But perhaps a plausible third variable.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html