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Overall
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CategoryInformation
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contactSee memleft.org for contact details!
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summaryThis dataset gives estimated membership for all leftist organizations in the US from 1848 to 2024 for which I can find plausible membership estimates.

This dataset enables researchers to quantitatively track the rise and fall of leftist organizations as social movement organizations (SMOs).

In particular, I hope that this dataset will enable researchers to track the effects of major events (such as the 2000's alter-globalization movement, post-2003 modern anti-war movement, 2008 Great Recession, and 2015-16 Sanders primary run) on leftist organizing.
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creditIndividuals who have provided great assistance: Alyaza B, Tim Davenport, David Duhalde, James Gregory.
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noteI've worked hard to provide the best estimates of membership over time for each organization, and best date for each estimate. A specific citation with a specific quote informs every single estimate. Common sources include: An org's own statement, a third party's estimate, an org's finances, an org's chapter count.

However, every estimate in this document should be taken as my best guesstimate at the most plausible date.
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interactiveMake some pretty graphs! https://memleftorg.shinyapps.io/MemLeftOrg/
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versionv2025-01-01
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Tabs
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Tab NameTab Summary
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membersprovides estimates of the membership: "date1" indicates the date of the estimate in YYYY-MM-DD; "type1" indicates ideology, "type2" indicates type of membership (total, dues-paying, cadre, etc.); "exclude" indicates whether I think the value should be excluded; "value" indicates the value (or "note" for interesting notes on organizational health); "group2" indicates organization name and "abbr" its abbreviation (for orgs with multiple name changes, the "main" one is given); "source_name" indicates the source used (from "sources" tab); "source_loc" provides the exact location of the estimate, usually with a quote; "notes1" and "notes2" indicate notes around reliability of estimate, date of estimate, etc. (these are very unorganized)
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sourcesprovides sources for the estimates: "abbr" indicates the main group estimated (if any), "source_name" indicates the short source name; "source_title" indicates the original title of the source; "url1" and "url2" indicate urls to the source; "notes1" and "notes2" indicate notes around reliability of source, lack of estimates, inability to access, etc. (these are very unorganized)
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other tabsthese tabs show my work for organizations with hard-to-estimate memberships; usually, my approach is to find some estimates of membership, find some estimates of number of chapters, then take the "average members per chapter" and multiply that by number of chapters
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Definitions
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NameDefinition
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type2The purpose of this dataset is both to provide raw estimates of membership over time AND some more refined estimates of the "power" of organizations over time, for which membership is a very useful proxy. For both questions, we are very interested in the "type" of membership in an organization. Due to lack of information and loss of information to history, it's often not possible to know exactly what kind of membership an organization reports. However, I've done my best to report membership according to the categories below:

1. Cadre: This membership level roughly means "someone working toward an organization with the intensity of a part-time or full-time employee". I think of this category as someone working around 10 or more hours of work per week. Revolutionary socialist organizations usually report their membership as "cadre", and are often able to achieve attendance rates of ~50% to ~80% to party congresses, indicating a high ability to turn out members. However, it's unclear how closely this notion of "cadre" maps onto my notion of "cadre". For some organizations, like the Black Panther Party, there was a small group of people working nearly 16/7 (~100 hours per week), maybe 100 of 1200 members; however, most members did not appear to contribute this level of activity. Most cadre organizations simply require attending weekly meetings and/or mass protests to keep cadre status (maybe ~3 hours per week), which is closer to the "active" definition below -- as a result, I routinely convert claims of "cadre" membership to "active" membership, except for a small number of organizations which demonstrated an extremely active membership (essentially the BPP, WUO, RNA, LWV, and staff-based organizations).

2. Active: This membership level roughly means "someone regularly volunteering for an organization". I think of this category as someone working 1+ hours per week. In general, in the absence of strong evidence of cadre-level activity, I tend to convert all claims of "party cadre" into "active" members. ("Claim no easy victories" and all.)

3. Paid: This membership level roughly means "someone currently paying dues for an organization". Dues-paying membership is, by far, the most commonly reported type of membership. Unfortunately, it is very hard to start from paid membership and estimate the number of members actively contributing to an organization. Some environmental organizations have millions of dues-paying members but a thousand or fewer volunteers. I'd guesstimate that this usually works as follows: Roughly 1 in 5 paid are active for explicitly socialist mass membership organizations, roughly 1 in 10 for leftist mass membership organizations, roughly 1 in 20 for political parties and old-style mutual aid groups.

4. MIGS: This membership level roughly means "dues-paying members plus those exempted from paying dues", from the phrase "Members in Good Standing". For example, this would include someone using a dues waiver during unemployment

5. Extra: This membership level roughly means "members in good standing plus some extra definition". For example, I gave this category to CPUSA's total membership estimates after 2000 (which includes online "joiners" that have never paid dues), to DSA's "constitutional" member count (which includes [usually former] members up to 2 years behind on dues), and SDS's non-paid members (who are not in good standing, but have some affiliation with the org).