reid@decwrl.dec.com (Brian Reid) (10/03/88)
USENET READERSHIP SUMMARY REPORT for Sep 88
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: 713 10989
Fraction reporting: 6.49% 100%
Users with accounts: 95277 1468000
Netreaders: 19699 303000
Average readers per site: 28
Percent of users who are netreaders: 20.68%
Average traffic per day (megabytes): 4.051
Average traffic per day (messages): 1846
Traffic measurement interval: last 28 days
Readership measurement interval: last 75 days
Sites used to measure propagation: 643
Valid data received from these sites:
3comvax abstl abvax.icd.abnet.com acer acheron acornrc actisb adelie
alembic aleytys alv alva amc-vlsi amdahl amdcad ames.arc.nasa.gov
amun-re andrew.cmu.edu anvil apple aramis.rutgers.edu arcadia ardent
ariel arisia arnor arran.tcom.stc.co.uk array arrow.garage.att.com
arrow.garage.nj.att.com arthur.cs.purdue.edu ascvax astroatc asylum
atari ateng atom atssc attdso axis b11 babbage balaena bandicoot banzai
basser bcd-dyn bcsfse beach.cis.ufl.edu bearcat.garage.nj.att.com beno
bentley.garage.att.com bentley.garage.nj.att.com beowulf.ucsd.edu
bigboy bio-image bjs black bms-at bnlux0 bnr-rsc bonnie.ics.uci.edu
brillig.umd.edu brspyr1 brushtail bsu-cs btnix bu-cs bu-it bu-tyng
bucasb bucsb bucsd buengc bute.tcom.stc.co.uk c3engr c3pe cacilj cad
cad.unsw.oz caelum caip.rutgers.edu calgary carola cascade catfish
catlabs cbterra cca ccng ccnysci cfisun cg-atla cgl.ucsf.edu
chalmers.se charlie chemabs cheviot.newcastle.ac.uk chinet chip cimcor
cit-vax cit-vlsi claris clinet clio cloud9 cmcl2 cnt cognos comdesign
concurrent.co.uk condor coplex cord.garage.att.com
cord.garage.nj.att.com cortex cos cosmo cp1 cpro crash credit
crete.cs.glasgow.ac.uk crick crin crocus cs-col.columbia.ncr.com
cs.hw.ac.uk cs.nott.ac.uk csadfa cseg csi csib csli csm9a csuchico
csuf3b csustan culdev1 cuuxb cvedg cxsea cybvax0 dahlia daisy daitc
daitc.daitc.mil dalcs dalcsug dandelion darth dasys1 dataspan dayton
dciem dcl-cs dcrlg1 ddsw1 ddtcg1 decuac decuac.dec.com deimos denning
desint devon dhw68k diamond.bbn.com didsgn dino
douglass.cs.columbia.edu drd drexel dri1 dri2 dsacg1 dsacg2 dsacg3
dsachg1 dsinc dukcds dukeac dukempd dvlmarv dycom earvax edison edrsys
edsel.garage.att.com edsel.garage.nj.att.com egvideo elan
elbereth.rutgers.edu elric elrond elroy elsie ems encore
eneevax.umd.edu enterprise.mtl.u-tokyo.junet entire
entropy.ms.washington.edu eos eplrx7 eplunix erix ernie.berkeley.edu
euler.rutgers.edu euraiv1 exec expya exunido eyeball fai fantasci
fedeva fermat.rutgers.edu ficc fico2 fishnet flab flatline fnatte
fortune gaboon gang-of-four garfield gatech gauss.rutgers.edu gcm geac
genrad geovision glacier gold gondor.cs.psu.edu gouldnl grand
granjon.garage.att.com granjon.garage.nj.att.com gray grebyn grian
gt5000 gtisqr gyre.umd.edu hacgate haddock.ima.isc.com hammer handel
hardees.rutgers.edu hardy harvisr haven.umd.edu hawaii.cs.glasgow.ac.uk
hawkmoon hcx1 helios herman hodge hqda-ai hscfvax hsi htc2 hurratio
husc4 hutch ico icot.jp icot32 ics.uci.edu idsssd igor iisat iitmax
ileaf ima.isc.com imagen inco infoac.rmi.de infofl.rmi.de infohh.rmi.de
io ipso.oz isaak iscuva iscuvb iscuvc iscuvd iscuve iscuvf isg300
islabs island itivax itrpe iuvax ivucsb izimbra.css.gov jackson
jarvis.csri jclyde jetson ji.berkeley.edu jimi.cs.unlv.edu juice
juniper kangaroo kaos karhu kazoo.cis.ohio-state.edu kodak kolvi korppi
kpd ksuvax1.cis.ksu.edu labrea lakesys lamc leah.albany.edu lehi3b15
leia lifia lily limerick lion ll1 ll1a lll-tis lll-winken logico
loglule looking lotus lsuc lxn lyra lzaz lzfmd lzfme lznv lzsc lzvlt
m2c maccs madnix magic mandrill mas1 math.rutgers.edu maynard mcdchg
mcf mcgill-vision mcgp1 mcmi meccsd medusa.cs.purdue.edu megatest
metasoft metavax mh.nl mhres mimsy.umd.edu mind minnow mipos2.intel.com
mipos3.intel.com miranda mit-eddie mmd1 mnetor mntgfx moogvax moscom
mrspoc mss mstar mtfmc mtfmi mtgzd mtgzf mtgzg mtgzi mtgzk mtgzm mtgzn
mtgzp mtgzq mtgzt mtgzy mtgzz mtunb mtund mtune mtunf mtung mtunh mtuni
mtunj mtunk mtunn mtuxj mtuxo mtxinu munsell murphy myrias nagano
nanovx natinst nbifet ncascade ncoast ncr-sd ncrats ncrcae
ncrcae.columbia.ncr.com ncrcpx ndmath ndsuvax nesac2 ness386
net.bio.net netsys newton.rutgers.edu nicmad nitro njin.rutgers.edu
noao noname novavax ns nttta nucleus nud occrsh octopus oddjob odyssee
ohsu-hcx olgb1 olivea oliveb olivee olivej oliven olivey omepd onfcanim
ontenv orca orchid orcisi orion.arc.nasa.gov orion.cf.uci.edu oscvax
osiris osiris.sics.se oswego.oswego.edu otter otto owlmnt oxtrap
pacbell packard.garage.att.com packard.garage.nj.att.com panda
paris.ics.uci.edu parsely pbhya pbhyb pbhyc pbhyd pbhye pbhyf pbhyg
pcrat pdn pedev pegasus percival petro phoenix phri
pierce.garage.att.com pierce.garage.nj.att.com pilot.njin.net pixar
polya polyof.poly.edu polyslo polyslo.calpoly.edu popeye poppy portia
poseidon possum potomac potoroo pr1me prcpto princeton prodix psc pte
ptsfa puck pwa-b pwcs pyr.gatech.edu pyramid pyrdc pyrman2 pyrnova
pyrps5 pyrtech pyrthoth qetzal qiclab qtc quick.com quokka radio rayssd
rayssdb rayssde rducky re.sics.se reed rel remus.rutgers.edu rencon
renoir.berkeley.edu resrch retix rhesus.primate.wisc.edu rhi rmi
rocky.oswego.edu rolls rose rosevax rti ruby rutgers.rutgers.edu sacred
sauron sauron.columbia.ncr.com scgvaxd scicom scobee sdcrdcf sdcsmb
sdcsvax sdn sdti se-sd serene shade shamash shark shasta shell sialis
sics.se sigma sigmast silver sirius.ua.oz sis siva smdvx1.intel.com
softway solaris soma sphinx.uchicago.edu splut spurge sq stanton
starfish starfish.convergent.com stb stcns3 stevie.cs.unlv.edu stride
studsys suadb sugar sultra suned1 sunybcs sw1e swan.ulowell.edu swatsun
swlabs t9103 tahoe.unr.edu td2cad teddy tekecs tekgvs teliut tellab5
teti tgate thor tiger titan.arc.nasa.gov tlxprs tmsoft tnosoes
toccata.rutgers.edu topaz.rutgers.edu tove.umd.edu toybox trillium
tropix ttidca tucos tut.cis.ohio-state.edu tybalt.caltech.edu tymix
ubvax.ub.com ucbarpa.berkeley.edu ucla-an ucqais.uc.edu ucsd.ucsd.edu
udiego ueda uhnix1 uhnix2.uh.edu uiucuxa uiucuxc ukecc ukma umd5
umd5.umd.edu umix.cc.umich.edu unicom unioncs uokmax uqcspe.oz utacs
utstat uunet uw-june uxe uxf van-bc vanuata.cs.glasgow.ac.uk vaxnix
versatc videovax.tek.com violet violet.berkeley.edu viper virgil
virginia viusys voder.nsc.com voodoo vrdxhq vsi1 vu-vlsi w3vh wa3wbu
wallaby watale watcgl watdaffy watdcsu watdewey watdonald watdragon
watelse water wateuler wathuey watlouie watmath watmum watopt
watscrooge watsol watson watvlsi watyew wb3ffv well westc wjvax wombat
wp3b01 wright xanth xicom xray yarra yendor yetti yunccn yunexus zap
zaphod zardoz zen ziebmef zinn zorch zycad
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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 10160 different sites in the Path lines of articles that
arrived at decwrl in the last 13 months. There are 5018
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 10160 sites,
84 (0%) are DEC E-net hosts not part of uucp, and
which therefore are not included in the 5018 figure.
Despite these various difficulties, I believe that 10989 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.
CROSSPOSTING PERCENTAGE: WHAT FRACTION OF THE ARTICLES ARE CROSSPOSTED
"Crossposting" means to post the same article simultaneously in more than one
newsgroup. In genuine "news" systems crossposting is implemented with Unix
links and does not increase the storage or transmisison cost, though in some
other systems crossposted articles are unbundled and must be stored and
transmitted separately.
The "crossposting percentage" is the percentage of the articles in this group
that are crossposted to at least one other group. If every article in this
group is crossposted, the percentage will be 100%; if none is crossposted,
then the percentage will be 0%. The crossposting percentage figure does not
take the size of the article into account, only the number of articles.
Crossposting a 50,000-byte article or a 50-byte article both cause the same
tally.
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 and computer costs to transmit this
newsgroup. The rate of $.0025 per kilobyte is the same value used in the
UUNET statistics reported biweekly. It is based on discussions among system
administrators about the true cost of news transmission.
The cost ratio is computed as follows:
$US/month/reader = ($USPerMonthPerSite * numberOfSites) / numberOfReaders
$USPerMonthPersite = KBytesTrafficPerMonth * $USPerKByte * Propagation factor
$USPerKByte = 0.0025
Combining all these gives
$USPerMonthPersite =
KBytesTrafficPerMonth * 0.0025
= KBytesTrafficPerMonth / 400
Therefore:
$US/month/reader =
(KBytesTrafficPerMonth * numberOfSites) / (400 * 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}!decwrl!reid