Author order looks like a single convention from the outside, but it is not one convention — it is at least three genuinely different systems that different fields treat as their default, and journals within a field can still deviate from it. A researcher moving between disciplines, or working on an interdisciplinary team, cannot assume the field they trained in sets the norm for a paper’s other authors. This guide covers the three dominant conventions, where each one is the norm, and how to avoid a dispute by agreeing on one explicitly and early.
This page is about how the order of names on the byline gets decided across fields. For what qualifies someone to be an author at all, see ICMJE’s four authorship criteria; for what a specific position on the byline (first, corresponding, senior/last, co-first) actually signals, see Types of Authorship in Research and the individual position terms linked throughout below.
Why there is no single convention
Neither the International Committee of Medical Journal Editors (ICMJE) nor the CRediT taxonomy (ANSI/NISO Z39.104-2022) specifies what order authors’ names should appear in. ICMJE’s criteria determine who qualifies as an author; CRediT records what each author did. Neither addresses where a qualifying author’s name sits in the list. That gap is filled entirely by disciplinary custom, journal house style, and, increasingly, explicit contribution statements published alongside the byline — which is exactly why the same set of contributions can be ordered in incompatible ways depending on which field’s convention is applied.
Alphabetical order: mathematics, economics, and some physics collaborations
In mathematics, alphabetical-by-surname order is overwhelmingly the norm: bibliometric analysis published in Scientometrics found alphabetical ordering in roughly 94% of multi-author mathematics papers when adjusted for the chance an alphabetical order occurs by coincidence, with even higher raw rates on two-author papers. The stated rationale is that co-authorship in these fields is treated as intellectually joint work, so ranking by contribution is considered both impractical to do fairly and beside the point — everyone’s name carries equal weight regardless of position.
Economics has historically followed the same alphabetical norm, but with a well-documented downside: research has shown alphabetical order confers a measurable citation and career advantage on authors whose surnames fall early in the alphabet, since they get listed (and often cited in short form, “Smith et al.”) first regardless of actual contribution. The American Economic Association’s response is a specific, real mechanism worth knowing about if you work in or alongside economics: its Author Randomization Tool lets co-authors generate a certified random order and mark the byline with the symbol “Ⓡ” (a circled R) to signal publicly that the order was randomized rather than either alphabetical or contribution-ranked — a solution proposed in Debraj Ray and Arthur Robson’s 2018 American Economic Review paper “Certified Random: A New Order for Co-Authorship.” Since roughly 2010, alphabetical ordering has been gradually declining across several fields that traditionally used it, including economics, education, philosophy, and mathematics, as more researchers move toward order that signals relative contribution instead.
Large multi-institutional collaborations in high-energy physics and astronomy add a third variant: with author lists running into the thousands (a 2015 joint ATLAS/CMS paper on the Higgs boson mass, published in Physical Review Letters, listed 5,154 authors across 24 pages of author and institution listings), ranking individuals by contribution is not attempted at all. These collaborations instead assign authorship collaboration-wide under the group’s own membership rules in effect at submission time, with names typically listed alphabetically or by a collaboration-defined convention rather than evaluated against a contribution hierarchy paper by paper.
First-author-did-most-work, senior-author-last: life sciences and biomedicine
Biomedical and life-science fields use a position-coded convention instead of an alphabetical one. The first author position is understood, by disciplinary custom rather than any formal rule, to signal the person who did the largest share of the hands-on work — running experiments, generating data, drafting the initial manuscript. The final, or last-author/senior-author, position is understood to signal the lab head, principal investigator, or most senior researcher who supervised the work and typically secured its funding, even though that person may have written comparatively little of the manuscript text themselves. Middle authors are read, informally, as contributing less than either end position, though this varies by paper and is not a formal ranking.
None of this is codified by ICMJE, which explicitly does not weigh in on order at all — it is entirely journal- and lab-culture convention, which is precisely why disputes over it are common. Several documented variations exist within this convention: co-first authorship, where two or more authors share the first position and a footnote states they contributed equally; a parallel co-senior/co-last-author convention using the same footnote logic at the other end of the byline; and the co-corresponding author convention, where the corresponding author role (who manages submission and post-publication correspondence) is split between two people rather than defaulting to whoever is first or last author. A person can also be named as a major contributor without occupying either the first or last position. See Resolving Authorship Order Disputes for what to do when this convention itself becomes the source of conflict, and Pros and Cons of Being First Author for what the position does and does not carry with it in practice.
Contribution-based ordering with explicit statements
A third approach keeps order meaningful by requiring it to directly track documented contribution, rather than relying on position alone to imply it. The American Psychological Association’s Ethics Code is explicit on this point: Standard 8.12b requires that “principal authorship and other publication credits accurately reflect the relative scientific or professional contributions of the individuals involved, regardless of their relative status,” and specifically states that holding a senior institutional position, such as a department chair, does not by itself justify authorship credit or a particular place in the order — see APA Authorship Guidelines.
A growing number of journals implement this by publishing a separate, plain-language author contributions statement alongside the byline, so that order and actual work are not left to be inferred from position at all. PNAS’s author-contributions statement, Nature’s author contributions statement, and PLOS ONE’s author contributions statement are three real, currently-used examples of this pattern — each requires authors to spell out who did what regardless of where their name falls in the list. CRediT’s optional “degree of contribution” qualifier (lead, equal, or supporting, attached to any of its 14 role categories) works the same way: it lets a contribution statement communicate relative weight within a role without forcing that information to be encoded solely through byline position. Large group authorship, where a collaboration or consortium is credited as a named entity with individual members listed separately, is a related but distinct mechanism — see Group Authorship.
Why this matters for interdisciplinary teams and researchers changing fields
None of the three conventions above is enforced by any funder, publisher-wide policy, or accreditation body — each is a norm specific to a field or sub-field, and norms do not travel automatically when a team crosses a disciplinary line. A biostatistician joining a physics collaboration, an economist co-authoring with a public-health team, or a computer scientist collaborating with a biomedical lab can each walk into a project assuming their home field’s default applies, only to find their co-authors assumed a different one. That mismatch is a common, avoidable source of the disputes covered in Resolving Authorship Order Disputes, and the Committee on Publication Ethics (COPE) guidance referenced there exists in large part because informal conventions, left unstated, fail exactly at the point where they are needed most.
The practical fix is procedural, not diplomatic: agree on an order convention explicitly, in writing, before most of the substantive work happens, rather than after a draft exists and positions feel fixed. A short written agreement at kickoff — which convention applies, how order will be revisited if contributions shift materially, and who is responsible for drafting the CRediT or journal-specific contributions statement — costs little and heads off the great majority of order disputes before they start.
Practical checklist for setting author order across disciplines
- Name the convention explicitly at project outset. Don’t assume everyone shares the same default; state whether the team is using alphabetical, first-did-most/senior-last, or strict contribution-ranked order.
- Put it in writing. A brief authorship agreement or team charter, even a shared document, prevents the most common source of later disagreement: differing memories of what was agreed informally.
- Complete a CRediT contribution statement regardless of which order convention is used. It documents actual work independently of position, which protects everyone if order itself is later disputed.
- Use equal-contribution markers (co-first, co-senior, co-corresponding) when genuinely warranted, and use them consistently with how the target journal defines and displays them.
- In alphabetical-norm fields with unequal contribution, consider a randomization tool like the AEA’s, or an explicit contributions statement, rather than silently ranking within an alphabetical list.
- Revisit order if contributions change substantially during a long project — order agreed at kickoff is not necessarily still accurate 18 months later.
- Check the target journal’s own authorship policy before submission. Journal house style can override field-wide default, and increasingly requires its own contributions statement regardless of what convention the byline itself follows.
Frequently asked questions
Does ICMJE require author order to reflect contribution?
No. ICMJE’s authorship criteria determine who qualifies as an author; the organization takes no position on what order qualifying authors’ names should appear in. Order is set entirely by disciplinary and journal convention, which is why it varies as much as it does.
Why do some papers list authors alphabetically even when contributions clearly differ?
In fields like mathematics and, historically, economics, alphabetical order is used specifically to avoid ranking co-authors at all — the convention treats listed authorship itself, not position within it, as the marker of contribution. This creates a known bias toward early-alphabet surnames, which is part of why mechanisms like the AEA’s randomization tool exist.
If my field orders by contribution, what does “co-first author” mean?
It signals that two or more people share the first-author position and are considered, by the authors’ and often the journal’s own account, to have contributed comparably to that top position — typically marked with a footnote such as “these authors contributed equally.” See Co-First Authorship for how this is documented and where it commonly appears.
Should the most senior person on a team always be listed last?
Only if the team is following the biomedicine-style senior-author-last convention, and only if that person’s role genuinely matches what the convention signals (supervision, funding, overall direction) — APA’s Ethics Code and CRediT-based contribution statements both explicitly reject seniority or institutional position alone as sufficient justification for authorship credit or placement.
What should a team do if collaborators from different fields disagree on the order convention?
Agree explicitly, in writing, before major work is underway, rather than defaulting silently to whichever collaborator’s field is more represented on the team. If disagreement persists once work is underway, follow a structured resolution process; see Resolving Authorship Order Disputes.
