# Separating, Filtering, Clarifying, Precipitating, and Still Machine Setters, Operators, and Tenders

US SOC code 51-9012. Markdown version of https://futurehistory.earth/timeline/51-9012

## In brief

In May 2025, [BLS](https://www.bls.gov/oes/special-requests/oesm25nat.zip) counted **60,100** US separating, filtering, clarifying, precipitating, and still machine setters, operators, and tenders, with median pay of **$51,610** a year. Of the BLS counts since 2003, the May 2025 count is the highest. The earliest figure here is [an estimate](https://en.wikipedia.org/wiki/Filter_press) of **40,000** from 1900, not measured the same way as today's count. The last full technology era in this work: Advanced process control, online analyzers, and remote monitoring, 2000 to 2020.

Figures: Official statistic (latest count and pay, highest count); Researched context (earliest figure).

## What the sources say

### Official outlook

BLS projects employment to decline 5.7% from 2025 to 2035. Source: [BLS Employment Projections 2025-35](https://data.bls.gov/projections/nationalMatrix?queryParams=51-9012&ioType=o) (Official statistic).

### AI exposure studies

- **0.88** estimated probability that the whole occupation could be computerised, over an unspecified number of years. Not a forecast of job losses. [Frey and Osborne, 2013](https://oms-www.files.svdcdn.com/production/downloads/academic/The_Future_of_Employment.pdf) (Official statistic)

### Since the 2013 prediction

In 2013, Frey and Osborne put this job's probability of computerisation at 0.88. BLS counted **42,510** of these jobs in May 2013 and **60,100** in May 2025 (+41%, a change derived by Future History). Figures: Official statistic.

Data as of BLS OEWS May 2025; BLS Employment Projections 2025-35. BLS publishes these counts as yearly survey snapshots and cautions against reading them as a precise trend. In May 2021 BLS changed how it estimates these counts (a model-based method using three years of survey data) and moved fully to the 2018 occupation codes, so part of a change across 2021 can come from the method rather than the work.

## Separating, Filtering, Clarifying, Precipitating, and Still Machine Setters, Operators, and Tenders employment and pay by year

- On record since: 1853
- Latest US employment: 60,100 (May 2025). Source: BLS OEWS May 2025 [3]
- Latest US median pay: $51,610 (May 2025). Source: BLS OEWS May 2025 [5]
- Outlook: -5.7% by 2035. Source: BLS Employment Projections 2025-35 [14]

### All 26 years of cited US data

| Year | US employment | Annual pay (median unless marked) | Source |
| --- | --- | --- | --- |
| 1900 | 40,000 (estimate) | n/a | Est., Wikipedia / Interfil [1] |
| 1920 | 75,000 (estimate) | n/a | Est., Oil [2] |
| 1956 | n/a | $5,200 (average) (estimate) | Est., Oil [4] |
| 2003 | 37,360 | $31,720 | BLS OEWS May 2003 [3] |
| 2004 | 38,000 | $33,230 | BLS OEWS May 2004 [3] |
| 2005 | 41,250 | $34,650 | BLS OEWS May 2005 [3] |
| 2006 | 43,660 | $34,970 | BLS OEWS May 2006 [3] |
| 2007 | 44,310 | $35,940 | BLS OEWS May 2007 [3] |
| 2008 | 41,200 | $36,690 | BLS OEWS May 2008 [3] |
| 2009 | 37,490 | $37,530 | BLS OEWS May 2009 [3] |
| 2010 | 38,050 | $37,840 | BLS OEWS May 2010 [3] |
| 2011 | 39,660 | $37,720 | BLS OEWS May 2011 [3] |
| 2012 | 41,430 | $38,570 | BLS OEWS May 2012 [3] |
| 2013 | 42,510 | $38,330 | BLS OEWS May 2013 [3] |
| 2014 | 43,310 | $38,590 | BLS OEWS May 2014 [3] |
| 2015 | 47,750 | $38,420 | BLS OEWS May 2015 [3] |
| 2016 | 47,160 | $38,360 | BLS OEWS May 2016 [3] |
| 2017 | 48,450 | $39,040 | BLS OEWS May 2017 [3] |
| 2018 | 49,770 | $40,810 | BLS OEWS May 2018 [3] |
| 2019 | 51,160 | $41,330 | BLS OEWS May 2019 [3] |
| 2020 | 47,930 | $43,100 | BLS OEWS May 2020 [3] |
| 2021 | 48,620 | $46,030 | BLS OEWS May 2021 [3] |
| 2022 | 52,470 | $46,250 | BLS OEWS May 2022 [3] |
| 2023 | 53,170 | $48,120 | BLS OEWS May 2023 [3] |
| 2024 | 54,200 | $49,500 | BLS OEWS May 2024 [3] |
| 2025 | 60,100 | $51,610 | BLS OEWS May 2025 [3] |

## Sources (69)

### Employment series

1. [Filter press history (Wikipedia) and centrifuge history (Interfil): industrial separation machinery adoption by 1900](https://en.wikipedia.org/wiki/Filter_press), Wikipedia / Interfil
2. [Oil, Chemical and Atomic Workers International Union (Wikipedia) -- founding 1918, grew to 30,000 members by 1921](https://en.wikipedia.org/wiki/Oil%2C_Chemical_and_Atomic_Workers_International_Union), Wikipedia
3. BLS OEWS, national cross-industry estimates (flat file), Bureau of Labor Statistics. Editions: [2003](https://www.bls.gov/oes/special-requests/oesm03nat.zip), [2004](https://www.bls.gov/oes/special-requests/oesm04nat.zip), [2005](https://www.bls.gov/oes/special-requests/oesm05nat.zip), [2006](https://www.bls.gov/oes/special-requests/oesm06nat.zip), [2007](https://www.bls.gov/oes/special-requests/oesm07nat.zip), [2008](https://www.bls.gov/oes/special-requests/oesm08nat.zip), [2009](https://www.bls.gov/oes/special-requests/oesm09nat.zip), [2010](https://www.bls.gov/oes/special-requests/oesm10nat.zip), [2011](https://www.bls.gov/oes/special-requests/oesm11nat.zip), [2012](https://www.bls.gov/oes/special-requests/oesm12nat.zip), [2013](https://www.bls.gov/oes/special-requests/oesm13nat.zip), [2014](https://www.bls.gov/oes/special-requests/oesm14nat.zip), [2015](https://www.bls.gov/oes/special-requests/oesm15nat.zip), [2016](https://www.bls.gov/oes/special-requests/oesm16nat.zip), [2017](https://www.bls.gov/oes/special-requests/oesm17nat.zip), [2018](https://www.bls.gov/oes/special-requests/oesm18nat.zip), [2019](https://www.bls.gov/oes/special-requests/oesm19nat.zip), [2020](https://www.bls.gov/oes/special-requests/oesm20nat.zip), [2021](https://www.bls.gov/oes/special-requests/oesm21nat.zip), [2022](https://www.bls.gov/oes/special-requests/oesm22nat.zip), [2023](https://www.bls.gov/oes/special-requests/oesm23nat.zip), [2024](https://www.bls.gov/oes/special-requests/oesm24nat.zip), [2025](https://www.bls.gov/oes/special-requests/oesm25nat.zip)

### Wage series

4. [Oil, Chemical and Atomic Workers International Union (Wikipedia) -- Canadian workers received wages close behind US levels after 1948; University of Missouri Libraries price/wage index context for 1950s manufacturing wages](https://en.wikipedia.org/wiki/Oil%2C_Chemical_and_Atomic_Workers_International_Union), Wikipedia
5. BLS OEWS, national cross-industry estimates (flat file), Bureau of Labor Statistics. Editions: [2003](https://www.bls.gov/oes/special-requests/oesm03nat.zip), [2004](https://www.bls.gov/oes/special-requests/oesm04nat.zip), [2005](https://www.bls.gov/oes/special-requests/oesm05nat.zip), [2006](https://www.bls.gov/oes/special-requests/oesm06nat.zip), [2007](https://www.bls.gov/oes/special-requests/oesm07nat.zip), [2008](https://www.bls.gov/oes/special-requests/oesm08nat.zip), [2009](https://www.bls.gov/oes/special-requests/oesm09nat.zip), [2010](https://www.bls.gov/oes/special-requests/oesm10nat.zip), [2011](https://www.bls.gov/oes/special-requests/oesm11nat.zip), [2012](https://www.bls.gov/oes/special-requests/oesm12nat.zip), [2013](https://www.bls.gov/oes/special-requests/oesm13nat.zip), [2014](https://www.bls.gov/oes/special-requests/oesm14nat.zip), [2015](https://www.bls.gov/oes/special-requests/oesm15nat.zip), [2016](https://www.bls.gov/oes/special-requests/oesm16nat.zip), [2017](https://www.bls.gov/oes/special-requests/oesm17nat.zip), [2018](https://www.bls.gov/oes/special-requests/oesm18nat.zip), [2019](https://www.bls.gov/oes/special-requests/oesm19nat.zip), [2020](https://www.bls.gov/oes/special-requests/oesm20nat.zip), [2021](https://www.bls.gov/oes/special-requests/oesm21nat.zip), [2022](https://www.bls.gov/oes/special-requests/oesm22nat.zip), [2023](https://www.bls.gov/oes/special-requests/oesm23nat.zip), [2024](https://www.bls.gov/oes/special-requests/oesm24nat.zip), [2025](https://www.bls.gov/oes/special-requests/oesm25nat.zip)

### Tool eras

6. [Filter press (Wikipedia) -- invention in the United Kingdom in 1853; Dehne filter press for sugar refining late 19th century](https://en.wikipedia.org/wiki/Filter_press), Wikipedia
7. [Oil Refining History -- first US petroleum still built by Samuel Kier, Pittsburgh, 1853](https://nexenpc.com/oil-refining-history-from-simple-distillation-to-complex-processes/), Next Energy Petroleum Company
8. [History of Industrial Centrifuges (Interfil) -- de Laval steam-powered centrifuge 1877 at 4,000 rpm; rapid commercial expansion through the 1890s](https://interfil.com.au/history-of-industrial-centrifuges-from-the-1700s-to-modern-day/), Interfil
9. [GEA Separation Technology -- 130 years of centrifuge history, Ramesohl and Schmidt 1893, continuous industrial applications](https://www.gea.com/en/stories/separate-from-the-rest/), GEA Group
10. [Distributed Control Systems History and Applications (Automation Community) -- DCS emerged from analog panel-board limitations of the 1960s-1970s](https://automationcommunity.com/distributed-control-systems-history-and-applications/), Automation Community
11. [Oil, Chemical and Atomic Workers International Union (Wikipedia) -- 80,000 members at 1999 dissolution vs. 210,000 in 1956](https://en.wikipedia.org/wiki/Oil%2C_Chemical_and_Atomic_Workers_International_Union), Wikipedia
12. [Evolution of Distributed Control Systems (Automate.org) -- APC and data analytics integrated in 1990s-2000s; remote monitoring enabled by Ethernet connectivity](https://www.automate.org/news/the-evolution-of-distributed-control-systems-dcs-from-legacy-architecture-to-intelligent-automation-109), Association for Advancing Automation
13. [O\*NET 51-9012.00 -- current tasks include monitoring instruments, examining samples for quality, turning valves to control flow (2024)](https://www.onetonline.org/link/summary/51-9012.00), O\*NET / BLS

### Forecasts and exposure studies

14. [BLS Employment Projections 2025-35, National Employment Matrix: 51-9012 Separating, filtering, clarifying, precipitating, and still machine setters, operators, and tenders (2025: 61.4 thousand; 2035: 57.9 thousand; -5.7%)](https://data.bls.gov/projections/nationalMatrix?queryParams=51-9012&ioType=o), Bureau of Labor Statistics
15. [Frey & Osborne (2013), "The Future of Employment: How Susceptible Are Jobs to Computerisation?", Appendix (SOC 51-9012 Separating, Filtering, Clarifying, Precipitating, and Still Machine Setters, Operators, and Tenders: probability 0.88, rank 517 of 702)](https://oms-www.files.svdcdn.com/production/downloads/academic/The_Future_of_Employment.pdf), Oxford Martin School, University of Oxford

### Historical notes

16. [Filter press (Wikipedia) -- Dehne filter press history; invention of filter press 1853 in the UK](https://en.wikipedia.org/wiki/Filter_press), Wikipedia
17. [History of Industrial Centrifuges (Interfil) -- de Laval steam-powered separator 1877 at 4,000 rpm](https://interfil.com.au/history-of-industrial-centrifuges-from-the-1700s-to-modern-day/), Interfil
18. [GEA Separation Technology -- 130 years of centrifuge history from Ramesohl and Schmidt 1893](https://www.gea.com/en/stories/separate-from-the-rest/), GEA Group
19. [Oil, Chemical and Atomic Workers International Union (Wikipedia) -- founding 1918, 30,000 members by 1921](https://en.wikipedia.org/wiki/Oil%2C_Chemical_and_Atomic_Workers_International_Union), Wikipedia
20. [Distributed Control Systems History and Applications (Automation Community) -- DCS introduced by Honeywell and Yokogawa in 1970s; refinery control-room consolidation in 1990s reduced operator headcount](https://automationcommunity.com/distributed-control-systems-history-and-applications/), Automation Community
21. [Why California refineries are closing (Stanford CEPP / California Senate briefing, 2026) -- California crude production fell 75% since the 1980s; refinery capacity declining since at least 1982](https://senv.senate.ca.gov/system/files/2026-02/supplemental-background-why-california-refineries-are-closing-stanford-cepp.pdf), Stanford CEPP / California Senate

### Predecessors & successors

22. [Oil Refining History (Next Energy Petroleum) -- early refinery workers were generalist laborers who learned still-operator skills on the job](https://nexenpc.com/oil-refining-history-from-simple-distillation-to-complex-processes/), Next Energy Petroleum Company
23. [Separator (milk) -- Wikipedia: milk separator history, gravity separation displaced by de Laval centrifuge in commercial dairies](https://en.wikipedia.org/wiki/Separator_%28milk%29), Wikipedia

### Present-day analysis

- [Eloundou et al. 2024 — GPTs are GPTs (Science)](https://arxiv.org/abs/2303.10130), accessed 2026-05-21
- [O\*NET 30.3 — US Department of Labor](https://www.onetcenter.org/database.html), accessed 2026-05-21

How to read these figures: https://futurehistory.earth/methodology. Every figure links to its own source; gaps stay gaps.