reid@decwrl.dec.com (Brian Reid) (01/02/88)
USENET READERSHIP SUMMARY REPORT for Dec 87
This is the first article in a monthly posting series from the Network
Measurement Project at the DEC Western Research Laboratory in Palo Alto,
California.
This survey is based on a sample of data taken from various USENET sites.
At the end of this message there is a short explanation of the measurement
techniques and the meaning of the various statistics. The messages that
follow this one show survey data sorted by various criteria.
The newsgroup volume and article counts that I post are often significantly
different from the ones posted by Rick Adams, because he includes the size of
a crossposted article in every group to which it is posted, whereas I charge
that size only to the first-named group.
The complete set of readership data (of which this is a summary) is posted
in news.lists. The software that will let your site participate in the
survey is in comp.sources.d and news.admin
Brian Reid
OVERALL SUMMARY:
This Estimated
Sample for entire net
Sites: 645 8400
Fraction reporting: 7.68% 100%
Users with accounts: 78614 1023000
Netreaders: 17633 229000
Average readers per site: 27
Percent of users who are netreaders: 22.43%
Average traffic per day (megabytes): 2.498
Average traffic per day (messages): 1123
Traffic measurement interval: last 21 days
Readership measurement interval: last 75 days
Sites used to measure propagation: 523
Valid data received from these sites:
16bits.dec.com 3comvax abstl abvax.abnet.com acad acheron acornrc
actisb adelie akov68.dec.com akov75.dec.com akov76.dec.com
akov88.dec.com alberta alliant amdahl amdcad ames
amsterdam.columbia.edu andrew.cmu.edu ant.dec.com apollo apple
aramis.rutgers.edu arran.tcom.stc.co.uk array arthur.cs.purdue.edu
ascvax astra astroatc atari ateng atom aurora auscso axis b11 baal
babbage bagels.dec.com banana.uq.oz basser bcd-dyn bcsfse bdmrrr
beach.cis.ufl.edu being.dec.com bellman beno beowlf.dec.com bigboy
black bms-at bnl bnr-rsc boole brand.usc.edu briar.philips.com brillig
brspyr1 bsu-cs bu-it bucasb bucsb bucsd buengc bute.tcom.stc.co.uk
cacilj cad.berkeley.edu cadomin cadsys.dec.com caeco caip.rutgers.edu
calgary calyx cascade casee.dec.com catlabs cavell cbterra cca ccng
cfisun cg-atla cgcha cgl.ucsf.edu cgofs.dec.com chalmers charlie
chemabs cheviot.newcastle.ac.uk child.dec.com chinet cimcor
cimnet.dec.com cit-vax cit-vlsi clinet clio cmcl2 cogito.dec.com cognex
cognos cogpsi concurrent.co.uk cookie.dec.com coplex cornell cortex cos
cp1 cpro crash crin cs.hw.ac.uk cs.nott.ac.uk csadfa cseg csi csib
cssaus.dec.com csuchico csustan culdev1 curie.dec.com curium.dec.com
cutter cuuxb cxsea cybvax0 daisy dalcs dalcsug dale dandelion darth
dasys1 davasun dayton dciem dcl-cs ddmtg1 ddsw1 decuac desint
devlab.dec.com devon dgis dhw68k diamond.bbn.com dickns.dec.com dkstar
drexel drra dsacg1 dsacg2 dsacg3 dsachg1 dscatl dukempd dvlmarv dycom
earvax ector.cs.purdue.edu edison edvax elan elbereth.rutgers.edu
elrond elroy elsie ems encore eneevax.umd.edu
enterprise.mtl.u-tokyo.junet ephemeral.ai.toronto.edu eplrx7 eplunix
eridan ernie.berkeley.edu ers eta euler.rutgers.edu exec expya exunido
fai fedeva felix fermat.rutgers.edu fizbin.dec.com flab focus fortune
forty2 fritz fstvax.dec.com fuksi galach.dec.com gang-of-four garfield
gatech gauss.rutgers.edu gcm geac gen1 genghis genrad genral.dec.com
gerbil.dec.com glacier glimmer gold gondor.cs.psu.edu gondor.psu.edu
gray grebyn grok.dec.com gvgpsa gyre.umd.edu haddock.ima.isc.com hadron
hammer hamstr.dec.com handel hardees.rutgers.edu harvisr hcx1 hechcx
helium helps heurikon hi hi.unm.edu hoptoad hoser.berkeley.edu
hpscad.dec.com hpwala hqda-ai hscfvax hsi husc4 husc7 hutch
iago.dec.com iaoobel ico icot32 icus igloo iisat ileaf ima imagen
imt3b2 indian.dec.com infinet infopro intrin ipso.oz iscuva iscuvb
iscuvc iscuvd iscuve islabs ism780c istg.dec.com ivory izimbra.css.gov
janis jarvis.csri.toronto.edu jasper ji.berkeley.edu jimi.cs.unlv.edu
jolnet jon.dec.com jplgodo kaos ki4pv killer klinzhai.rutgers.edu kodak
kolvi korppi krebs l5comp labrea lafite.dec.com lakesys lamc laura
leadsv.leads.lmsc.com leah.albany.edu leia lerouf.dec.com lifia lily
lindy liuida ll1 ll1a lll-tis lll-winken loglule looking lsuc
lucy.dec.com lzaz lznv lzsc lzwi maccs madnix mancol mandrill mas1
math.rutgers.edu maxwell maynard mcdchg mcf mcgill-vision mck-csc
meccsd meccts megatest mendel metasoft mhres mimsy mind minnow miramon
mit-eddie mitsumi mnetor mntgfx moogvax mordred.cs.purdue.edu moscom
mosys mrstve mstar mtgzy mtgzz mtunb mtund mtune mtunf mtung mtunh
mtuni mtunj mtunk mtunl mtuxo mtx5a mtx5c mtx5d mtx5e mtxinu munsell
musky2 myrias navajo nbifet nbires ncoast ncr-sd ncrats ncrcae ncrcpx
ndmath ndsuvax necntc nesac2 netsys neumann newton.rutgers.edu
nexus.dec.com nicmad noao novavax nttlab nuchat nucleus nusdhub oblio
obsess.dec.com occrsh occrsh.att.com octopus oddjob oddput odyssee
olgb1 olgba olivea oliveb olivee olivej oliven omepd ondine onecom
onfcanim opus orca orchid orion.arc.nasa.gov orion.arpa oscvax osiris
otto owlmnt ozvax panda parsely paul.rutgers.edu pbhya pbhyb pbhyc
pbhyd pbhye pbhyf pbhyg pcrat pdn pegasus percival peregrine phoenix
phoenix.princeton.edu phri piaget pixar plus5 polecat polyslo popeye
popvax portnoy poseidon potomac princeton psuvax1.psu.edu psy.vu.nl
ptsfa pvab pwa-b pwcs pyr pyramid pyrdc pyrps5 pyrtech qaz_pn qetzal
qiclab qtc quest questar quick radio rayssd rayssdb rayssde re
remus.rutgers.edu rencon renoir.berkeley.edu retix rgb.dec.com
rhesus.primate.wisc.edu rhi rmi rochester rocky romed rosevax
rsts32.dec.com rtech rti ruby rutgers.rutgers.edu ryenat sandia sandoz
sauron sbo scgvaxd scicom scoman.dec.com sdcrdcf sdcsmb sdcsvax sdn
sdti se-sd shamash shark shasta shell shire.dec.com sialis sics sigma
sigmast sis sjfc slxsys small-u sneaky soma sphinx.uchicago.edu splut
sq ssdevo.dec.com sstat starfish stb stcns3 stevie.cs.unlv.edu stl
stratus stride suadb sugar sunybcs sw1e swan.cs.ulowell.edu
swan.ulowell.edu swatsun swlabs t9103 tahoe.unr.edu tallis.dec.com
td2cad teddy tekecs tekgvs teliut tellab5 temvax terak terminus tesla
teti tfh.dec.com thelink thundr.dec.com titan.arpa tmsoft
toccata.rutgers.edu topaz.rutgers.edu toroid.dec.com tove.umd.edu
trancept tropix trwrb trwrb.dsd.trw.com trwspf ttidca tucos turtlevax
tut.cis.ohio-state.edu tutor twitch tybalt.caltech.edu tymix ubvax
ucbarpa.berkeley.edu ucla-an ucqais udiego ufqtp ugdist uhnix1 uhnix2
uiucuxc uiucuxf ukecc ultra.dec.com umd5 umix.cc.umich.edu unicus
uokmax uop uqcspe.oz utacs uthelios utstat uunet uvabme uxa uxe van-bc
vaxwaller vianet video.dec.com videovax.tek.com violet.berkeley.edu
viper virgil virginia viusys voder voder.nsc.com voodoo vrdxhq vu-vlsi
wa3wbu watale watcgl watdaisy watdcsu watdragon wateng water watmath
watt watvlsi watyew wb3ffv well westend.columbia.edu whyvax.dec.com
wiley wjvax wookie.dec.com wp3b01 wright wyse1 xanth xicom xray xray2
yendor yetti yumath zap zaphod zinn zorch
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EXPLANATION OF THE MEASUREMENTS AND STATISTICS
Survey data is taken by having one person at each site run a program called
"arbitron", which looks at the news or notes files and determines the
newsgroups that the user has read within a recent interval. To "read" a
newsgroup means to have been presented with the opportunity to look at at
least one message in it. Going through a newsgroup with the "n" key counts
as reading it. For a news site, "user X reads group Y" means that user X's
.newsrc file has marked at least one unexpired message in Y. If there is no
traffic in a newsgroup for the measurement period, then the survey will show
that nobody reads the group. For a notes site, "user X reads group Y" means
that user X has been in the notesfile with the sequencer in the last 14 days.
The "14 days" interval for notesfiles corresponds to "unexpired" for news.
The "arbitron" program is periodically posted to comp.sources.d, or is
available from me (decwrl!reid). The notesfiles version of the program should
be available through standard notesfiles software distribution channels as
well.
SITES SURVEYED IN THIS SAMPLE
"This Sample" means the set of sites that have sent in an arbitron report
within the past "Readership measurement interval" days. In every case the
most recent report from each site is used. At the moment, some of the
readership reports are several months old. In future postings those reports
will have expired and will not be included.
One might argue that the sample is self-selected, and thereby be biased. It
does in fact have a certain self-selection factor in it, because we only get
data from sites at which someone participates in the survey. However, we do
not require the participation of every user at a site, only one user. The
survey program returns data for every user on the system on which it was run.
Since there are an average of 30 people per site reading news, there is a
certain amount of randomness introduced that way. Of course, the sample is
biased in favor of large sites (they are more likely to have a user willing
to run the survey program) and software-development-oriented sites (more
likely to have a user *able* to run the survey program).
NETWORK SIZE
I determine the network size by looking at the set of sites that are
mentioned in the Path lines of news articles arriving at decwrl. This number
is consistently higher than the number of sites that posted a message (as
measured and posted from uunet) because it includes passive sites that are
on the paths between posting sites and decwrl. Each month I store the names
of the hosts that are named that month, and for this report I used the past
13 months worth of data.
There are 8373 different sites in the Path lines of articles that
arrived at decwrl in the last 13 months. There are
different sites in the comp.mail.maps data, but comp.mail.maps includes every
site that participates in uucp; there is a considerable number of machines
that exchange uucp mail but do not get USENET. Of those 8373 sites,
51 (0%) are DEC E-net hosts not part of uucp, and
which therefore are not included in the figure.
Despite these various difficulties, I believe that 8400 is the best
estimate for the size of USENET. Because it is actually a measurement of the
number of sites that have posted a message or that are on the path to a site
that has posted a message, it will be slightly smaller than the number of
sites that actually read netnews. Any site that believes it is not being
counted can just ensure that it posts at least one message a year, so that
it will be counted.
NUMBER OF USERS
The number of users at each site is determined in a site-specific fashion.
Sometimes it is done by counting the number of user accounts that have
shells and login directories. Sometimes it is done by counting the number of
people who have logged in to the machine in some interval. Sometimes other
techniques are used. This number is probably not very accurate--certainly
not more accurate than to within a factor of two.
ESTIMATED TOTAL NUMBER OF PEOPLE WHO READ THIS GROUP, WORLDWIDE
There are two sources of error in this number. The number is computed by
multiplying the number of people in the sample who actually read the group by
the ratio of estimated network size to sample size. The estimated total can
therefore be biased by errors in the network size estimate (see above) and
also by errors in the determination of whether or not someone reads a group.
Assuming that "reading a group" is roughly the same as "thumbing through a
magazine", in that you don't necessarily have to read anything, but you have
to browse through it and see what is there, then the measurement error will
come primarily from inability to locate .newsrc files, which can either be
protected or moved out of root directories. There is no way of measuring the
effect on the measurements from unlocated .newsrc files, but it is not likely
to be more than a few percent of the total news readers.
PROPAGATION: HOW MANY SITES RECEIVE THIS GROUP AT ALL
This number is the percent of the sites that are even receiving this
newsgroup. The information necessary to compute propagation was not generated
by early versions of the arbitron program, so the "basis" (number of sites)
used to generate the Propagation figure is smaller than the "Sites in this
sample" figure. A site's data will be used to compute propagation if either
(a) it reports zero readers for at least one group, or (b) it is using an
arbitron with an explicit version number that is high enough.
MESSAGES PER MONTH AND KILOBYTES PER MONTH
Traffic is measured at decwrl, in Palo Alto, California. Any message that has
arrived at decwrl within the last "Traffic measurement interval" days is
counted, regardless of when it was posted. Monthly rates are computed by
taking the total traffic, dividing by the number of days in the traffic
measurement interval, and multiplying by 30. Decwrl runs 2.10.3 news, which
does not store the "Date-Received", "Relay-version" or "Posting-version"
header lines; the amount of space occupied at your site might be higher, and
the number of bytes transmitted between machines is probably higher. By
definition this number is correct, because it is an exact measurement, but it
may differ from the traffic at your site by as much as 15% due to timing
differences and news version differences. Timing differences will be random,
but will average out in the long run. News version differences will cause a
systematic error that is additively uniform across all newsgroups, and which
therefore does not significantly affect ratios.
If a message is crossposted to several groups simultaneously, it is charged
only to the first-named group in the list. Note that this differs from the
statistics posted from uunet every 2 weeks: the uunet data charge a message
equally to every group that it is crossposted to.
PARTICIPATION RATIO: MESSAGES per MONTH per 1000 READERS
This number is exactly what it says: the number of messages per month in
that newsgroup, divided by the number of 1000 readers. It is an indication
of how involved the readers of the group are in the traffic, of whether they
are mostly listeners or mostly talkers. Its accuracy is limited by the
accuracy of its two components. The messages per month figure is exact; the
reader count is only as accurate as the network size estimate, which is in
worst case accurate to 40%. Therefore you should treat this number as having
an error margin of plus or minus 40%. However, ratios between participation
ratios for different newsgroups are quite accurate, since the network-size
component divides out.
COST RATIO: DOLLARS PER MONTH PER READER
The most controversial field in the survey report is the "$US per month per
reader". It is the estimated number of dollars that are being spent on
behalf of each reader, worldwide, on telephone costs to transmit this
newsgroup. The cost ratio does not include the cost of disk storage to store
the news or of computer time to process it; both of those are assumed to be
free.
The cost ratio is computed as follows:
$US/month/reader = ($USPerMonthPerSite * numberOfSites) / numberOfReaders
$USPerMonthPersite = KBytesTrafficPerMonth * $USPerKByte * Propagation factor
$USPerKByte = ($USperMinute / KBytesPerMinute) * (1 - CompressionFactor)
$USperMinute = 0.10 [ten cents per minute avg phone cost]
KBytesPerMinute = 60 * BytesPerSecond / 1000
BytesPerSecond = 100 [average transfer rate over 1200-baud line]
CompressionFactor = 0.4 [40% compression is typical for netnews]
Combining all these gives
$USPerMonthPersite =
KBytesTrafficPerMonth * (0.10 / 6) * (1 - 0.4)
= KBytesTrafficPerMonth / 100
Therefore:
$US/month/reader =
(KBytesTrafficPerMonth * numberOfSites) / (100 * numberOfReaders)
The accuracy of this number is in fact better than the accuracy of the
participation ratio, because the source of error--the network size
estimate--is present both in the numerator and the denominator, and therefore
cancels out. The primary source of bias in this number comes from the bias in
the "estimated number of readers, worldwide", which is described above. Treat
this value as being accurate to within about 25%.
SITE PARTICIPATION
I would like to receive data from every site on USENET. The arbitron programs
(posted comp.sources.d along with this report) work on news 2.9, 2.10.[1-3],
2.11, and on many versions of notesfiles.
Brian Reid
DEC Western Research Laboratory, Palo Alto CA
reid@decwrl.DEC.COM
{ihnp4,allegra,decvax,ucbvax,sun,pyramid,cbosgd}!decwrl!reid