[ppml] Combining Forecasts

On 29-aug-2007, at 11:10, <michael.dillon at bt.com>  
<michael.dillon at bt.com> wrote:

> Combining forecasts by averaging them has been shown to improve the
> accuracy of forecasting. Perhaps it is time to dig some of the other
> forecasts out of the woodwork so that we have more than just Tony's  
> and
> Geoff's work.

Here's mine. Please note that the numbers I'm about to mention are  
based on the dayly RIR allocation reports that I download from their  
FTP servers a few times a week. You can peruse this information  
yourself at http://www.bgpexpert.com/addrspace.php but caveats apply;  
also see http://www.bgpexpert.com/addrspace2005.php and http:// 
www.bgpexpert.com/addrspace2006.php .

On january first, 2005, the total free address space (= free in the  
global IANA pool and the space delegated to RIRs by IANA, but not to  
LIRs/ISPs/end-users by RIRs) was 97.4 /8s. A year later it was 87.5  
and on january first, 2007, it was 77.5. So we've been using up  
pretty much exactly 10 /8s a year in 2005 and 2006.

Today the free space is 69.8 /8s. And interestingly, earlier this  
year a legacy /8 was returned to the IANA pool, something that hasn't  
happened for many years. So in 8 months (2/3s of a year) we've been  
using up either 7.7 or 8.7 /8s, depending on how you count that  
reclaimed block while 6.7 would have been expected during such a  
period based on the last two years. So that's a 15 to 30 % increase  
in yearly address use. Let's project this into the future, and  
include a stable 11 /8s a year option just for kicks:

                 0%            15%           30%
            used   free   used   free   used   free
2008-1-1:  11.0   67.5   11.5   66.0   13.0   64.5
2009-1-1:  11.0   56.5   13.2   52.8   16.9   47.6
2010-1-1:  11.0   45.5   15.2   37.6   21.9   25.7
2011-1-1:  11.0   34.5   17.5   20.1   28.4   -2.7
2012-1-1:  11.0   23.5   20.1    0.0
2013-1-1:  11.0   12.5
2014-1-1:  11.0    1.5

So if nothing happens, we have until about valentine's day 2014, but  
if we have a new trend on our hands it's either new year 2012 or late  
2010. However, the yearly address consumption has never shown clear  
trends that keep going for more than a few years. What often happens  
is that there is a sudden increase from one year to the next, and  
then a decrease or stagnation in the year after. So I don't think  
we'll see a consistent 30% trend, or even a 15% one. I'd say there's  
a 25% chance we'll run out in 2011, a 40% chance that it's 2012 and a  
25% chance it's 2013.