reid@decwrl.DEC.COM (Brian Reid) (11/01/87)
USENET READERSHIP SUMMARY REPORT for Oct 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: 589 8300
Fraction reporting: 7.10% 100%
Users with accounts: 75565 1064000
Netreaders: 16779 236000
Average readers per site: 28
Percent of users who are netreaders: 22.20%
Average traffic per day (megabytes): 2.245
Average traffic per day (messages): 1069
Traffic measurement interval: last 21 days
Readership measurement interval: last 75 days
Sites used to measure propagation: 446
Valid data received from these sites:
16bits.dec.com 3comvax abstl abvax.abnet.com acornrc adelie agora
akelei akov68.dec.com akov75.dec.com akov76.dec.com alberta alliant alv
amdahl amdcad ames amsterdam.columbia.edu ant.dec.com apollo apple
aqua.dec.com aramis.rutgers.edu argus arran.tcom.stc.co.uk array
arthur.cs.purdue.edu ascvax asd.dec.com asic.dec.com astra astroatc
atari ateng athena atom atssc aurora ausmelb axis bagels.dec.com
banana.cs.uq.oz banana.uq.oz basser bdmrrr beno beowulf.ucsd.edu bigboy
binkly.dec.com black bms-at bnr-rsc brand.usc.edu briar.philips.com
brillig brspyr1 bsu-cs bu-cs bu-it bucasb bucket bucsb bucsb.bu.edu
bucsd buengc bute.tcom.stc.co.uk cad.berkeley.edu cadomin
caip.rutgers.edu calyx camlot.dec.com cantuar cascade casee.dec.com
casetek caus-dp cavell cbterra cca ccng ccvaxa celica.dec.com
cesare.dec.com cfisun cg-atla cgcha cgl.ucsf.edu cgofs.dec.com chalmers
charlie chemabs cheviot.newcastle.ac.uk chinet ci-dandelion cimcor
cit-vax cit-vlsi clinet clio cmcl2 cognex cognos cogpsi
concurrent.co.uk cornell cortex cos cp1 cpro crin cs.hw.ac.uk
cs.nott.ac.uk csadfa csm9a csustan culdev1 cullvax curium.dec.com
cutter cuuxb cvl cwruecmp cxsea dalcs dalcsug dale darth dasys1 davasun
dayton dciem dcl-cs ddsw1 decuac decwet.dec.com decwrl desint
devlab.dec.com devon dgis dhw68k diamond.bbn.com diehrd.dec.com dlb
drexel drra dsacg1 dsacg2 dsacg3 dscatl dssdev.dec.com dukempd dutesta
dvlmarv dycom earvax ecrcvax ector.cs.purdue.edu edison elan
elbereth.rutgers.edu elrond elroy elsie ems encore eneevax.umd.edu
eplrx7 eplunix erlang.dec.com ernie.berkeley.edu ers esc-bb eta ethos
ethz euler.rutgers.edu eur3b2 euraiv1 exec2 fai fdcv01.dec.com fedeva
felix fermat.rutgers.edu firqb.dec.com fizbin.dec.com fortune
forty2.dec.com fritz gang-of-four garfield gatech gauss.rutgers.edu gcm
geac genghis genrad geovision glacier gondor gondor.psu.edu
goons.dec.com grebyn gt-stratus gvgpsa haddock.ima.isc.com
haddock.isc.com hadron hammer handel harvisr hawk.cs.ulowell.edu hcx1
hechcx helium helps hi hillst.dec.com hnsurg3 hoptoad
hoser.berkeley.edu hpscad.dec.com hpwala hqda-ai hscfvax hurratio husc4
husc7 husc8 hutch hwcs iago.dec.com iaoobel ichaya ico igloo ihf1 ileaf
ima imagen imt3b2 inco infinet ingr intrin invest ipso.oz iscuva iscuvb
iscuvc iscuvd iscuve islabs ism780c izimbra.css.gov jasper
ji.berkeley.edu jimi.cs.unlv.edu jplgodo kaoa01.dec.com ki4pv killer
klinzhai.rutgers.edu kodak kolvi korppi kpd kpdc krebs labrea lakesys
lamc lando.dec.com leia lemon.berkeley.edu lifia lily lindy lion liuida
lll-tis lll-winken lln-cs looking lotus lzaz lznv lzsc lzwi macbeth
maccs madnix mandrill mapper mas1 math.rutgers.edu maynard mcdchg
mcgill-vision mck-csc meccsd meccts megatest metavax mhres mimsy mind
minnow mit-eddie mitsumi mnetor mntgfx moogvax mordred.cs.purdue.edu
moscom mss mstar mtblue.dec.com mtgzy mtgzz mtunb mtund mtune mtunf
mtung mtunh mtuni mtunj mtunk mtunl mtxinu munsell myrias naakka
nac.dec.com navajo navion.dec.com nbifet nbires ncoast ncr-sd ncrats
ncrcae ncrcpx ncsuvx ndsuvax necntc netsys newton.rutgers.edu
nexus.dec.com nibroc nicmad noao novavax nttlab nuchat nucleus nucsrl
nutmeg.dec.com oblio obsess.dec.com oddjob olivea oliveb olivee olivej
oliven omepd onecom opus orca orchid orion.arpa osiris oulu owf owlmnt
oxtrap panda parsely paul.rutgers.edu pbhya pbhyb pbhyc pbhyd pbhye
pbhyf pcrat pdn pegasus percival peregrine phdvax.dec.com phoenix
phoenix.princeton.edu phri piaget pixar plaid plus5 pluto pogo polecat
popeye popvax portnoy poseidon princeton psuvax1 psuvax1.psu.edu ptsfa
puck pyr pyramid pyrdc qetzal qiclab qtc quad1 quick radio rayssd
rayssdb rayssde re regent.dec.com remsit remus.rutgers.edu
renoir.berkeley.edu retix rhi rmi rochester rocky rolf rose rosevax
rtech rti ruby russell rutgers.rutgers.edu sandia sandoz sarin sauron
scanf.dec.com scgvaxd scicom sdcsvax sdn sdti se-sd seiph shark shasta
shell sics sigma sis sjfc slxsys sneaky soma sphinx splut sri-spam
starfish stb stl stratus suadb subsys.dec.com sunybcs sw1e
swan.cs.ulowell.edu sweeny.dec.com t9103 tahoe tallis.dec.com td2cad
teddy tekecs teklds tellab5 temvax terak terminus tesla teti
tfh.dec.com tiger tkov58.dec.com tle.dec.com tmsoft toccata.rutgers.edu
toklas.dec.com topaz.rutgers.edu tove.umd.edu tri-x tropix trwspf
tsg.dec.com ttidca tucos turtlevax tut.cis.ohio-state.edu tutor
tybalt.caltech.edu tymix ubvax ucbarpa.berkeley.edu uccba udiego ufqtp
ugdist uhnix1 uhnix2 uiucuxa uiucuxc uiucuxe uiucuxf ukecc
ultra.dec.com umb umd5 umd5.umd.edu umix.cc.umich.edu umn-cs unrvax
uokmax uop uqcspe.oz usceast usiv03.dec.com utacs uthelios
utopie.dec.com utradio utstat uunet uvabme uw-june uw-larry uw-vlsi uxa
uxe van-bc vaxtrain vianet video.dec.com violet.berkeley.edu voder
voodoo vrdxhq vu-vlsi wanginst watale watarts watcgl watdaisy watdcsu
watdragon wateng water watmath watmum watopt watsol watvlsi well
wheaton wiley wnuxb wp3b01 wsl.dec.com wyse1 xanadu.dec.com xanth xray2
yendor yetti yippee.dec.com zap zaphod zeus zgov03.dec.com 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). I intend to post,
reasonably soon, some breakdowns of statistics about the sites that have
responded.
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 Seismo) 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 8220 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 8220 sites,
56 (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 8300 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.
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
$USPerKByte = ($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 to net.sources 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,glacier}!decwrl!reid