reid@decwrl.dec.com (Brian Reid) (08/01/88)
USENET READERSHIP SUMMARY REPORT for Jul 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: 751 9207
Fraction reporting: 8.16% 100%
Users with accounts: 91963 1127000
Netreaders: 18984 232000
Average readers per site: 25
Percent of users who are netreaders: 20.64%
Average traffic per day (megabytes): 4.044
Average traffic per day (messages): 1809
Traffic measurement interval: last 28 days
Readership measurement interval: last 75 days
Sites used to measure propagation: 606
Valid data received from these sites:
16bits.dec.com 3comvax 4gl.nl abstl abvax.abnet.com abvax.icd.abnet.com
abyss.dec.com acer acheron acornrc actisb adelie alberta alembic
aleytys alv alva amc-vlsi amdahl amdcad ames.arc.nasa.gov amun-re
andrew.cmu.edu ant.dec.com anvil apollo apple aramis.rutgers.edu
arcadia ariel arnor arran.tcom.stc.co.uk array arrow.garage.nj.att.com
arthur.cs.purdue.edu ascvax ashok.dec.com aspen2.dec.com astroatc
asylum atari ateng atlact.dec.com atom atssc aurora axis b11 babbage
bacchus bandicoot banzai bartle.dec.com basser bcd-dyn bcsfse
beach.cis.ufl.edu bearcat.garage.nj.att.com beno
bentley.garage.nj.att.com bigboy bjs black bms-at bnlux0 bnr-rsc
bonnie.ics.uci.edu briar.philips.com brillig.umd.edu brspyr1 brushtail
bsu-cs btnix bu-it bu-tyng bucasb bucsb bucsd buengc bunker
bute.tcom.stc.co.uk c3engr c3pe cacilj cad cad.dec.com cad.unsw.oz
cadomin cadse.dec.com caelum caip.rutgers.edu calgary carola cascade
catfish catlabs cavell cbterra cca ccng ccnysci ceetm1 cfisun cg-atla
cgl.ucsf.edu chalmers chalmers.se charlie chemabs
cheviot.newcastle.ac.uk chgv04.dec.com child.dec.com chinet chip
cimamt.dec.com cimnet.dec.com cit-vax cit-vlsi claris clinet clio
clt.dec.com cmcl2 cnt comdesign concurrent.co.uk condor cookie.dec.com
coplex cord.garage.nj.att.com cortex corum cos cosmo cp1 cpro cpsc6b
crash creamy crete.cs.glasgow.ac.uk crick crin cs-col.columbia.ncr.com
cs.hw.ac.uk cs.nott.ac.uk csadfa cseg csi csib csinn csli csm9a csuf3b
csustan culdev1 curium.dec.com cxsea cybvax0 daisy daitc dalcs dalcsug
dandelion darth dasys1 dataspan dayton dcl-cs ddsw1 ddtcg1
decsim.dec.com decuac decvax.dec.com decwet.dec.com decwin.dec.com
decwrl.dec.com denning desint devcim.dec.com devlab.dec.com devon
dhw68k diamond.bbn.com dino douglass.columbia.edu
douglass.cs.columbia.edu dpdmai.dec.com drexel dri1 dri2 dsacg1 dsacg2
dsacg3 dsachg1 dscatl dsinc dssdev.dec.com dukempd dvlmarv dycom earvax
eastend.columbia.edu edison edrsys 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 eridan erlang.dec.com
ernie.berkeley.edu euclid.dec.com euler.rutgers.edu eur3b2 euraiv1 exec
expya fai fantasci fdcv06.dec.com fedeva fermat.rutgers.edu fico2 flab
flatline fnatte fortune gaboon gang-of-four garfield
gargoyle.uchicago.edu gatech gauss.rutgers.edu gcm geac genrad
giamem.dec.com glacier goby.dec.com gold gondor.cs.psu.edu gouldnl
granjon.garage.nj.att.com gray grebyn grian gt5000 gyre.umd.edu
haddock.ima.isc.com hadron hammer handel hardees.rutgers.edu hardy
harvisr hawaii.cs.glasgow.ac.uk hawkmoon helios herman hi-csc
hi.unm.edu hodge home hpscad.dec.com hqda-ai hscfvax hsi hurratio husc4
husc7 hutch ibmpa.pasc.ibm.com ico icot32 ics.uci.edu idsssd iitmax
ileaf ima ima.isc.com imagen imt3b2 inco indian.dec.com infinet io
ipso.oz iscuva iscuvb iscuvc iscuvd iscuve iscuvf isg100 islabs island
istg.dec.com itivax itrpe izimbra.css.gov jackson jaimes.dec.com
jarvis.csri jasper jclyde jetson jfcl.dec.com ji.berkeley.edu
jimi.cs.unlv.edu jon.dec.com jonlab jrdvax.dec.com jumbo juniper
kangaroo kaoa01.dec.com kaos karhu klinzhai.rutgers.edu kodak kolvi
korppi kpd kylie labrea lakesys lamc leah.albany.edu lehi3b15 leia
leman.dec.com lifia lily lindy lithium ll1 ll1a lll-tis lll-winken
logico loglule looking lownlab lsuc lucy.dec.com lxn lzaz lzfmd lzfme
lznv lzsc m2c maccs madnix maestro mandrill mas1 math.rutgers.edu
maynard mcdchg mcf mcgill-vision mcmi meccsd meccts
medusa.cs.purdue.edu megatest metasoft metavax mh.nl mhres
mildew.dec.com mimsy.umd.edu mind minnow mipos2 mipos2.intel.com mipos3
mipos3.intel.com mips miranda mit-eddie mmd1 mnetor mntgfx moogvax
mosart moscom 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 mtwain.dec.com mtx5c mtx5e mtxinu
munsell musky2 mvcad3.dec.com myrias n8ino nac.dec.com nacad.dec.com
nagano natinst navajo nbifet ncoast ncr-sd ncrats ncrcae
ncrcae.columbia.ncr.com ncrcpx ndmath ndsuvax nesac2 ness386 netsys
newton.rutgers.edu nexus.dec.com nicmad nitro njin.rutgers.edu noao
noname novavax nttlab nttta nuchat nucleus nud occrsh octopus oddjob
oddput 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 otishq
otter otto owlmnt oxtrap packard.garage.nj.att.com panda
park.columbia.edu parsely pbhya pbhyb pbhyc pbhyd pbhye pbhyf pbhyg
pcrat pdn pedev pegasus peregrine pernod.dec.com phoenix
phoenix.princeton.edu phri pierce.garage.nj.att.com pilot.njin.net
pixar polya polyof.poly.edu polyslo popeye portia poseidon possum
potomac potoroo prcpto princeton prodix psc psuhcx psuvax1.cs.psu.edu
psy.vu.nl ptsfa puck pvab pwa-b pwcs pyr pyr.gatech.edu pyramid pyrdc
pyrman2 pyrnova pyrps5 pyrtech pyrthoth qetzal qiclab qtc quark.dec.com
quick.quick.com quokka radio rainbo.dec.com rancho.dec.com
rangly.dec.com rayssd rayssdb rayssde rdvax.dec.com re.sics.se redwood
reed remus.rutgers.edu rencon renoir.berkeley.edu retix rgb.dec.com
rhesus.primate.wisc.edu rhi riverside.columbia.edu rmi rocky.oswego.edu
rolls rosevax rsts32.dec.com rti ruby rutgers.rutgers.edu sales.dec.com
sandoz sauron sauron.columbia.ncr.com scenic.dec.com scgvaxd scicom
scobee scoman.dec.com sdcrdcf sdcsmb sdcsvax sdn sdti se-sd shade
shamash shark shasta shell shire.dec.com sialis sics.se sigma sigmast
sirius.ua.oz sis siva skylrk.dec.com smdvx1 smdvx1.intel.com sneaky
sniff.dec.com softway solaris soma sphinx.uchicago.edu splut sq
ssdevo.dec.com starfish stb stcns3 stereo.dec.com stevie.cs.unlv.edu
stride studsys suadb sugar sunybcs sw1e swan.ulowell.edu swatsun swlabs
t9103 tahoe.unr.edu td2cad teddy tekbspa tekecs tekgvs teliut tellab5
teti tfh.dec.com thor thundr.dec.com titan.arc.nasa.gov tle.dec.com
tmsoft tnosoes toccata.rutgers.edu topaz.rutgers.edu tove.dec.com
tove.umd.edu tropix tsc.dec.com ttidca tucos tunatx.dec.com
tybalt.caltech.edu tymix ubvax.ub.com ucbarpa.berkeley.edu ucla-an
ucqais ucsd.ucsd.edu ufqtp uhnix1 uhnix2 uhnix2.uh.edu uisc1 uiucuxa
uiucuxc ukecc ukma ultra.dec.com umd5 umix.cc.umich.edu unicom uokmax
uqcspe.oz usceast usmrw2.dec.com utacs utstat uw-june uxe uxf
valkyr.dec.com vanuata.cs.glasgow.ac.uk vector video.dec.com
videovax.tek.com violet.berkeley.edu viper virgil virginia viusys
voder.nsc.com voodoo vrdxhq vsi1 vu-vlsi w3vh wa3wbu watale watcgl
watdaffy watdcsu watdewey watdonald watdragon water wathuey watlouie
watmath watscrooge watson watvlsi watyew wb3ffv well widgit
winery.dec.com wjvax wombat wookie.dec.com wp3b01 wright wuphys xanth
xicom xray yarra yendor yetti yoda.dec.com york.columbia.edu yunccn
yunexus zap zaphod 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 9133 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 9133 sites,
80 (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 9207 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