Power-Law Distributions in Empirical Data

Aaron Clauset, Cosma Rohilla Shalizi, M. E. J. Newman · SIAM Review / arXiv · 2009 · statistics · 10.1137/070710111 · record clauset2009-power-law-data
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Where this record's text came from. faceted 2026-08 by reading the locally held text (pdftext); every evidence string verified as an exact substring of that text before merging. The method tag is imperfect: the paper is a statistical-methods paper whose validation is simulation on synthetic data (which is what the quoted sentence supports), but it also performs a large empirical reanalysis of 24 published data sets, which the offered vocabulary has no term for. Note the quoted contradicts evidence reads '3.16 0.06' because the PDF extraction lost the plus-minus sign, which is moved to the end of the sentence in the source text; the quote is verbatim as the article text stands. The paper also critiques the standard practice of fitting power laws by least squares on log-log histograms, but that is a critique of a general practice rather than of a named study, so it is not recorded as a claim_relation. 2026-08-14, 2026-08-16 and 2026-08-25 schema-0.3 passes: every quote verified as an exact substring of the staged text and anchored at merge time; concept terms verified present; every edge endpoint an existing node.
How to read this page. The article itself is not reproduced here — this paper is not cleared for redistribution, so what follows is the tag layer alone. The evidence sentences are withheld with the article. The table at the foot lists every tag the record carries; each row names the facet it belongs to, and the whose words column says whether the tag records the paper's own wording or the tagger's sentence about the paper. Every tag links to each other paper in the corpus carrying it. The machine-readable edition of the same thing is the TEI file beside this one, where the tags live in standOff, and the article is at its publisher via the link below. When we have changed our mind. Some entries in the table begin with a word in capitals and the reason for it. EVIDENCE CORRECTED — the finding still stands, but we had quoted the wrong sentence from the paper, and the quotation has been replaced with the right one. RETRACTED — the entry itself was wrong; it stays on the page, marked, with the reason, rather than being deleted. WITHDRAWN AND REPLACED — the entry was wrong, and a corrected version of it appears in the entries below. Each mark carries its own reason, in brackets, because the reasons differ from one entry to the next. An entry we have WITHDRAWN is removed from this page and kept in the record, with its reason. A line reading Audit and a date is a later re-reading of the entry against its whole sentence: DOUBTFUL means it was kept, and the reason says what is loose about it. Quotation marks inside the tagger's sentence. Where a tag is the tagger's own sentence, a phrase in quotation marks inside it is borrowed from the paper — the tagger's wording around it is not. The paper's own sentence is the evidence quote for that row; on this page it is withheld with the article, and the article is at its publisher. Nothing inside quotation marks anywhere on this page is ours: if it is quoted, it is the paper's. Whose words a concept carries. A concept entry records a term the paper itself uses, so the term, the sense given for it, and its evidence are the paper's own words, quoted where the paper fixes them. This is the opposite of a sense entry in the tag table, which is the tagger's sentence about how the paper uses a term. Where a concept entry could not be grounded in the paper's words, the entry says so on its own row.
Other fields define these differently the same word, defined another way in another discipline
sample-size 5 fields · null-hypothesis 3 fields · standard-deviation 3 fields · confidence-interval 2 fields · simulation 2 fields · statistical-significance 2 fields · and 2 more →

Tags on this paper

Every tag the record carries, each linking to every other paper in the corpus that carries it. A tag appears here whether or not its words occur in the article — the spans below are only the ones a sentence in this paper licenses. Of the 9 concept tags on this paper, 6 are grounded in a quoted sentence.
power law maximum likelihood goodness of fit heavy tail model selection scaling parameter xmin likelihood ratio test log-normal the lower bound of the power-law range is chosen by minimising the Kolmogorov-Smirnov distance between the empirical distribution and the best-fit model above that bound - too high a bound shrinks the data and too low a one includes non-power-law points, so the minimum lies between each synthetic data set is scored against ITS OWN best-fit power law rather than against the distribution it was drawn from, which is what makes the resulting p-value unbiased: the synthetic sets undergo exactly the calculation the real data underwent, fitting included synthetic data are generated semiparametrically - drawn from the fitted power law with probability equal to the observed tail fraction, and otherwise resampled from the observed points below the cut-off - so the synthetic sets share the empirical body while following the power law in the tail the test distribution is constructed to be hard rather than convenient: it is exponential below the cut-off and a power law above, and its slope is CONTINUOUS at the cut-off, so it deviates only gently from the power law below that point - the authors' word is challenging uncertainty on the fitted parameters is obtained by a nonparametric bootstrap - drawing a fresh sequence of n points uniformly at random from the original data and re-estimating both the lower bound and the scaling parameter on each surrogate set the alternative goodness-of-fit statistics are tested rather than assumed: reweighted KS and Kuiper behave like plain KS, while Anderson-Darling returns cut-offs an order of magnitude too large, and the cost of that conservatism is stated as fewer tail observations, larger error on the scaling parameter and less ability to validate the model the number of synthetic data sets is fixed by the precision wanted in the p-value rather than by convention, derived from the test's expected worst-case performance the direction of the p-value is inverted relative to its ordinary use: the quantity being tested is the model the authors want to assess rather than a null, so a HIGH p-value is the favourable one and a low value rules the power law out power-law distribution exponent goodness-of-fit Kolmogorov-Smirnov heavy-tailed tail empirical data tail of the distribution lower bound xmin goodness-of-fit statistic quantity x Bayesian confidence-interval confidence interval hypothesis-testing hypothesis test mean Mean of null-hypothesis null hypothesis p-value regression linear regression sample-size sample size standard-deviation standard deviation standard-error standard error statistical-significance statistically significant variance simulation

Legend

relation to other workclaim_relationshow this paper stands to another: agrees, contradicts, extends, qualifies
claim typeclaim_typethe shape of the claim: existence, mechanism, method, critique, prediction, null
concept edgeconcept_edgesan asserted relation between two concepts, with the sentence asserting it
conceptconceptsan idea the paper works with, quoted where the paper uses it
content tagcontent_tagsa finding, definition, quantity, statistic or variable named in the paper
controlcontrolsan experiment run to eliminate a rival explanation
limitationlimitationswhat the paper says its evidence cannot support
mechanismmechanismshow the reported effect is said to come about
methodmethodhow the paper produced its evidence
phenomenonphenomenonthe effect or regularity under study
sensesensesa distinct use of a term, quoted where the paper fixes it
transfertransfersa method or concept carried in from another field

The paper

The full text is not reproduced here. This article is not cleared for redistribution, so the page carries the tag layer only. Its evidence sentences are withheld; the grounding status remains with each tag, and the article itself is at https://doi.org/10.1137/070710111. The reading view exists for the papers whose licence permits it.

Every tag on this page

claim_relations 3 · claim_type 1 · concept_edges 3 · concepts 6 · content_tags 28 · controls 3 · limitations 12 · mechanisms 8 · method 1 · phenomenon 1 · senses 3 · transfers 1

Relations on this page carry a quotation for the claim. Where a relation was separately evidenced — and so tested against the vocabulary for its type — the row says so; none of 3 relations here carry that mark. The rest are the tagger’s reading of the sentence quoted beside them.

facettagfieldconf.whose words
claim_typemethod
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claim_typethe paper's words
phenomenonpower-law distributions in empirical data
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phenomenonthe paper's words
methodsimulation
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also in: simulation
methodthe paper's words
mechanismsmechanisms
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mechanisms[0]0.85the tagger's words
mechanismsmechanisms
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mechanisms[1]0.95the tagger's words
mechanismsmechanisms
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mechanisms[2]0.95the tagger's words
mechanismsmechanisms
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mechanisms[3]0.85the tagger's words
mechanismsmechanisms
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mechanisms[4]0.85the tagger's words
mechanismsmechanisms
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mechanisms[5]0.85the tagger's words
mechanismsmechanisms
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about this quote: 2026-08-16: THIS QUOTE IS TRUNCATED BECAUSE THE FORMULA IT LEADS TO IS UNREADABLE IN THE STAGED TEXT. The pdftext extraction flattens the expression for the required number of synthetic data sets out of order - the staged body reads 'at least 1 2 synthetic data sets' with '4 e-' appearing separately - so the rule the sentence states cannot be quoted verbatim without quoting nonsense. The span stops at the last readable words. The paper's own worked example (accuracy to two decimal digits requiring about 2500 sets) is likewise in the damaged region and is deliberately NOT reproduced here, because I would be typing it rather than cutting it.
mechanisms[6]0.95the tagger's words
mechanismsmechanisms
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mechanisms[7]0.85the tagger's words
limitationsone can never confirm a power law, only find data consistent with it
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what this limits: every power-law claim anywhere: Quotation withheld - the hypothesis cannot be confirmed
limitations[0]the tagger's words
limitationsfew empirical phenomena obey power laws across the whole range of x
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what this limits: the range over which any fitted power law holds: Quotation withheld
limitations[1]the tagger's words
limitationsKnown sampling biases in several of the reanalysed data sets were left uncorrected.
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what this limits: the reanalyses in this paper: WE HAVE NOT ATTEMPTED TO CORRECT ANY BIASES IN OUR ANALYSIS
limitations[2]the tagger's words
limitationsMany of the reanalysed data sets are partial samples of larger populations.
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what this limits: the datasets reanalysed: MANY OF THESE DATA SETS ARE ONLY SUBSETS OF MUCH LARGER ENTITIES (SUCH AS THE WEB SITES, WHICH ARE ONLY A SMALL FRACTION OF THE ENTIRE WEB)
limitations[3]the tagger's words
limitationsThe framework is presented only for the power law; no extension to other distributional forms is given.
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what this limits: the applicability of the framework: IT COULD ALSO BE EXTENDED TO OTHER, NON-POWER-LAW DISTRIBUTIONS ... ALTHOUGH WE HAVE NOT GIVEN SUCH AN EXTENSION HERE
limitations[4]the tagger's words
limitationsThe procedure often cannot separate power-law from log-normal behaviour.
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what this limits: any claim that a power law rather than a log-normal has been found: IT IS EXTREMELY DIFFICULT TO TELL THE DIFFERENCE BETWEEN LOG-NORMAL AND POWER-LAW BEHAVIOR
limitations[5]the tagger's words
limitationsTwo model forms indistinguishable on the observed data can give enormously different extrapolations into the tail, which is where such fits are usually applied.
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what this limits: extrapolating any of these fits to large rare events: the paper states conclusions from different fitted forms can differ enormously while being indistinguishable on the data
limitations[6]1.0the tagger's words
limitationsSeven of the twenty-four data sets previously conjectured to be power laws are firmly ruled out.
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what this limits: any of the seven named data sets as power-law distributed: HTTP connections, earthquakes, web links, fires, wealth, web hits and the metabolic network are ruled out here
limitations[7]1.0the tagger's words
limitationsTwo published scaling parameters for the same citation data disagree with each other and with this paper's maximum-likelihood estimate.
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what this limits: a published scaling exponent for a data set: for these citation data three different values are in print, and the paper says the earlier two are incompatible with the maximum-likelihood estimate
limitations[8]1.0the tagger's words
limitationsThe accept/reject verdict rests on a stated p-value threshold of 0.1.
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what this limits: the power-law verdicts in this paper: they follow a p-value threshold of 0.1, and cases near it are decided by that choice
limitations[9]1.0the tagger's words
limitationsThe range fitted is chosen, and that choice controls how much data the test sees.
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what this limits: the sample size behind any of these fits: xmin is estimated, and it determines how many points enter the test
limitations[10]1.0the tagger's words
limitationsErrors run in both directions on small samples: a power law can look like a good fit to non-power-law data, and true power laws cannot be separated from alternatives.
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what this limits: a power-law fit on a small sample in either direction: the paper states both false acceptance and failure to discriminate occur there
limitations[11]1.0the tagger's words
transfersthe fitting procedure is deliberately applied across twenty-four data sets from unrelated branches of enquiry, so that the method rather than any one field's data is what is tested
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transfers[0]0.9the tagger's words
controlsa goodness-of-fit p-value computed for the power law AND for each plausible competing distribution, and the two compared
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eliminates: that the power law fits because heavy-tailed data fits almost any heavy-tailed form - a log-normal or a stretched exponential may fit as well or better, and only comparing them shows which · outcome (stated by the tagger, no quotation): held
controls[0]0.95the tagger's words
controlsan explicit rejection rule fixed in advance: p greater than 0.1 keeps the power-law hypothesis, otherwise it is rejected
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eliminates: that the decision to accept a power law is made after seeing how good the fit looks · outcome (stated by the tagger, no quotation): held
controls[1]0.95the tagger's words
controlsthe whole procedure was run on SYNTHETIC data drawn from known distributions
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eliminates: that the method itself is wrong - synthetic data has a known answer, so the procedure can be checked against ground truth before it is trusted on real data · outcome (stated by the tagger, no quotation): held
controls[2]0.95the tagger's words
conceptspower law
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also in: power law
concepts[0]the paper's words
conceptsmaximum likelihood
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concepts[1]the paper's words
conceptsscaling parameter
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concepts[5]the paper's words
conceptsxmin
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also in: xmin
concepts[6]the paper's words
conceptslikelihood ratio test
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concepts[7]the paper's words
conceptslog-normal
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also in: log-normal
concepts[8]the paper's words
sensespower law - a hypothesis one can only fail to reject; the paper says an observed quantity can rarely if ever be certified as power-law distributed
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senses[0]1.0the tagger's words
sensespower law - a property of the tail only, holding above a chosen minimum rather than across the whole range
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senses[1]1.0the tagger's words
sensesscaling parameter - a quantity whose published values for one data set disagree, because they depend on the estimator used
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senses[2]1.0the tagger's words
claim_relationscontradicts → previously claimed power laws in the literature
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claim_relations[0]the tagger's words
claim_relationscontradicts → previously reported scaling parameters for the citation distribution of [48], namely 2.9 in [62] and 2.5 in [33]
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claim_relations[1]the tagger's words
claim_relationsbuilds-on → Ijiri and Simon [28] and Mitzenmacher [42] on the limits of characterising empirical distributions
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claim_relations[2]the tagger's words
concept_edgespower law —contrasted-with→ log-normal
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strength of the relation: 1 Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the p-value supports a classification as power-law, log-normal or undecided; contrasted-with is loose.
also in: power law · log-normal
concept_edges[0]the tagger's words
concept_edgesscaling parameter —operationalised-as→ maximum likelihood
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strength of the relation: 1 Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span compares reported scaling parameters with 'our maximum likelihood figure'; operationalised-as is loose.
concept_edges[1]the tagger's words
concept_edgesxmin —part-of→ power law
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strength of the relation: 1
also in: xmin · power law
concept_edges[2]the tagger's words
content_tags24 — real-world data sets tested for power-law fit
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content_tags.quantities[0]the tagger's words
content_tags2 < α < 3 — typical range of the scaling parameter
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content_tags.quantities[1]the tagger's words
content_tags8226 — average US city/town/village population (2000 Census)
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content_tags.quantities[2]the tagger's words
content_tags180 — typical adult male American height (near-Gaussian example)
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content_tags.quantities[3]the tagger's words
content_tags2 — largest deviations in a well-behaved distribution
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content_tags.quantities[4]the tagger's words
content_tagsleast-squares fitting yields substantially inaccurate power-law parameters
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content_tags.findings[0]the tagger's words
content_tagstheir framework combines maximum likelihood with KS goodness-of-fit
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content_tags.findings[1]the tagger's words
content_tagssome conjectured power laws are ruled out by the data
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content_tags.findings[2]the tagger's words
content_tagspower laws usually hold only above a minimum value xmin
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content_tags.findings[3]the tagger's words
content_tagsscaling parameter
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content_tags.variables[0]the tagger's words
content_tagslower bound xmin
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content_tags.variables[1]the tagger's words
content_tagsgoodness-of-fit statistic
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content_tags.variables[2]the tagger's words
content_tagsquantity x
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also in: quantity x
content_tags.variables[3]the tagger's words
content_tagspower law
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also in: power law
content_tags.definitions[0]the tagger's words
content_tagsscaling parameter
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content_tags.definitions[1]the tagger's words
content_tagstail of the distribution
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content_tags.definitions[2]the tagger's words
content_tagsBayesian
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also in: Bayesian
content_tags.statistics[0]the tagger's words
content_tagsconfidence-interval
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content_tags.statistics[1]the tagger's words
content_tagshypothesis-testing
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content_tags.statistics[3]the tagger's words
content_tagsmean
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also in: mean
content_tags.statistics[4]the tagger's words
content_tagsnull-hypothesis
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content_tags.statistics[5]the tagger's words
content_tagsp-value
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also in: p-value
content_tags.statistics[6]the tagger's words
content_tagsregression
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also in: regression
content_tags.statistics[7]the tagger's words
content_tagssample-size
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about this quote: QUOTE REPAIRED: the extractor split a hyphen-space and the quote was recorded faithfully with the damage in it, which made it unanchorable. The repaired string is an EXACT SUBSTRING of the staged text - that is why it was accepted, not because a rule produced it. The text as originally recorded is kept in evidence as extracted.
also in: sample-size
content_tags.statistics[8]the tagger's words
content_tagsstandard-deviation
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content_tags.statistics[9]the tagger's words
content_tagsstandard-error
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about this quote: QUOTE RECOVERED FROM THE PAPER'S OWN CHARACTERS. The recorded quote was LETTERS-ONLY IDENTICAL to this stretch of the staged text but not an exact substring of it - spaces, hyphens, ligature glyphs or mathematical operators differed, so it could never anchor. This is the file's own text between the same two letters: not produced by a rule about the damage, copied out of the file. Round-trip checked (the recovered span is letters-only equal to the original) and length-checked. The text as originally recorded is kept in evidence as extracted.
content_tags.statistics[10]the tagger's words
content_tagsstatistical-significance
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content_tags.statistics[11]the tagger's words
content_tagsvariance
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also in: variance
content_tags.statistics[12]the tagger's words

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