# Construction Managers

US SOC code 11-9021. Markdown version of https://futurehistory.earth/timeline/11-9021

Also called: Project manager construction, Construction project manager, General contractor, Construction superintendent, Site manager construction.

## In brief

In May 2025, [BLS](https://www.bls.gov/oes/special-requests/oesm25nat.zip) counted **380,360** US construction managers, with median pay of **$114,990** 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/Norcross_Brothers) of **50,000** from 1880, not measured the same way as today's count. The last full technology era for construction managers: Cloud-based construction management platforms, 2012 to 2022.

## What the sources say

### Official outlook

BLS projects employment to grow 9.1% from 2025 to 2035. Source: [BLS Employment Projections 2025-35](https://data.bls.gov/projections/nationalMatrix?queryParams=11-9021&ioType=o).

### AI exposure studies

- **40%** of this job's tasks are exposed to large language models. Not a forecast of job losses. [Eloundou and others, 2023](https://github.com/openai/GPTs-are-GPTs/blob/main/data/occ_level.csv)

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.

## Construction Managers employment and pay by year

- On record since: 1864
- Latest US employment: 380,360 (May 2025). Source: BLS OEWS May 2025 [5]
- Latest US median pay: $114,990 (May 2025). Source: BLS OEWS May 2025 [14]
- Outlook: +9.1% by 2035. Source: BLS Employment Projections 2025-35 [30]

### In other countries

The latest figure each country's statistics agency publishes for this job. Each uses its own occupation definition, survey basis and currency, so the numbers are not directly comparable with each other or with the US figures.

- **Canada** (NOC 70010)
  - Employment, 2020: 88,725. Source: Statistics Canada Census 2021 [8]. Statistics Canada Census of Population 2021: number of persons with employment income in NOC 70010 Construction managers, Canada, reference year 2020. A recipients basis (anyone with employment income during the year), slightly broader than a point-in-time employed count. Statistics Canada Open Licence.
  - Median pay, 2020: C$89,000. Source: Statistics Canada Census 2021 [18]. Statistics Canada Census of Population 2021 (Table 98-10-0586): median employment income for NOC 70010 Construction managers, Canada, reference year 2020, full-year full-time workers (the basis comparable to the US OEWS full-time median). Statistics Canada Open Licence.
- **United Kingdom** (UK SOC 1122)
  - Employment, 2025: 102,000. Source: ONS ASHE 2025 [9]. ONS Annual Survey of Hours and Earnings (Table 14): employee jobs in SOC 1122 Production managers and directors in construction, United Kingdom, 2025 (ASHE "number of jobs", thousands x1000; excludes self-employment). Open Government Licence v3.0.
  - Median pay, 2025: £54,947. Source: ONS ASHE 2025 [19]. ONS Annual Survey of Hours and Earnings (Table 14.7a): median gross annual pay for all employee jobs in SOC 1122 Production managers and directors in construction, United Kingdom, 2025. Open Government Licence v3.0.
- **Australia** (ANZSCO 1331)
  - Employment, 2025: 128,300. Source: ABS Labour Force Survey [10]. ABS Labour Force Survey (Detailed), table EQ08: employed persons in ANZSCO 1331 Construction Managers, national (summed across sex and state/territory), annual average of 4 quarterly estimates.
  - Median pay, 2025: A$195,052. Source: ABS Employee Earnings May 2025 [20]. Annualised (x52) from A$3,751 median weekly earnings. ABS Survey of Employee Earnings and Hours, May 2025: median pay for full-time non-managerial employees paid at the adult rate, before tax. Surfaced via the Jobs and Skills Australia occupation profile.

### All 30 years of cited US data

| Year | US employment | Annual pay (median unless marked) | Source |
| --- | --- | --- | --- |
| 1880 | 50,000 (estimate) | n/a | Est., Norcross Brothers [1] |
| 1920 | 200,000 (estimate) | n/a | Est., US Census Bureau [2] |
| 1950 | 300,000 (estimate) | n/a | Est., US Census Bureau [2] |
| 1960 | n/a | $8,500 (estimate) | Est., University of Missouri Libraries [11] |
| 1980 | n/a | $28,000 (estimate) | Est., FRED / BLS [12] |
| 1982 | 210,000 (estimate) | n/a | Est., Wikipedia / CMAA [3] |
| 2000 | 229,200 | $58,250 | BLS OEWS 2000 [4] |
| 2003 | 196,110 | $66,470 | BLS OEWS May 2003 [5] |
| 2004 | 185,580 | $69,870 | BLS OEWS May 2004 [5] |
| 2005 | 192,610 | $72,260 | BLS OEWS May 2005 [5] |
| 2006 | 207,630 | $73,700 | BLS OEWS May 2006 [5] |
| 2007 | 216,120 | $76,230 | BLS OEWS May 2007 [5] |
| 2008 | 220,550 | $79,860 | BLS OEWS May 2008 [5] |
| 2009 | 204,760 | $82,330 | BLS OEWS May 2009 [5] |
| 2010 | 191,430 | $83,860 | BLS OEWS May 2010 [5] |
| 2011 | 195,000 | $84,240 | BLS OEWS May 2011 [5] |
| 2012 | 207,580 | $82,790 | BLS OEWS May 2012 [5] |
| 2013 | 213,720 | $84,410 | BLS OEWS May 2013 [5] |
| 2014 | 227,710 | $85,630 | BLS OEWS May 2014 [5] |
| 2015 | 239,640 | $87,400 | BLS OEWS May 2015 [5] |
| 2016 | 249,650 | $89,300 | BLS OEWS May 2016 [5] |
| 2017 | 263,480 | $91,370 | BLS OEWS May 2017 [5] |
| 2018 | 278,460 | $93,370 | BLS OEWS May 2018 [5] |
| 2019 | 293,380 | $95,260 | BLS OEWS May 2019 [5] |
| 2020 | 285,640 | $97,180 | BLS OEWS May 2020 [5] |
| 2021 | 284,750 | $98,890 | BLS OEWS May 2021 [5] |
| 2022 | 303,220 | $101,480 | BLS OEWS May 2022 [5] |
| 2023 | 329,190 | $104,900 | BLS OEWS May 2023 [5] |
| 2024 | 348,330 | $106,980 | BLS OEWS May 2024 (employment) [5]; BLS OEWS May 2024 (pay) [15] |
| 2025 | 380,360 | $114,990 | BLS OEWS May 2025 [5] |

## Sources (110)

### Employment series

1. [Norcross Brothers — Wikipedia (firm founding 1864, 1,000+ employees by 1886; context for 1880 workforce scale)](https://en.wikipedia.org/wiki/Norcross_Brothers), Wikipedia / various construction history sources
2. [US Census Bureau — Occupational Trends in the United States 1900 to 1950 (construction industry employment history)](https://www.census.gov/library/publications/1958/demo/occupational-trends-1958.html), US Census Bureau
3. [Construction Management Association of America — Wikipedia (CMAA founded 1982)](https://en.wikipedia.org/wiki/Construction_Management_Association_of_America), Wikipedia / CMAA
4. [BLS OES 2000 national estimates (flat file)](https://www.bls.gov/oes/special-requests/oes00nat.zip), Bureau of Labor Statistics
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)
6. [Statistics Canada, Census of Population 2006, Table 97-563-XCB2006069 (Wage and salary statistics by occupation, NOC-S 2006), income reference year 2005](https://www12.statcan.gc.ca/census-recensement/2006/dp-pd/tbt/Rp-eng.cfm?LANG=E&PID=96285), Statistics Canada
7. [Statistics Canada, Census of Population 2016, Table 98-400-X2016356 (Occupation by employment income statistics, NOC 2016), income reference year 2015](https://www150.statcan.gc.ca/n1/en/catalogue/98-400-X2016356), Statistics Canada
8. [Statistics Canada, Census of Population 2021, Table 98-10-0586 (Employment income statistics by occupation unit group, NOC 2021), income reference year 2020](https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=9810058601), Statistics Canada
9. ONS: Annual Survey of Hours and Earnings, Table 14.7a (Annual pay - Gross), 4-digit SOC 1122, United Kingdom. Office for National Statistics, Annual Survey of Hours and Earnings, Table 14. Licensed under the Open Government Licence v3.0., Office for National Statistics. Editions: [2002](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2002/2002-table-14.zip), [2006](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2006consistentw_007methodology/2006-table-14.zip), [2010](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2010revised/2010-revised-table-14.zip), [2011](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2011revisedbasedonsoc2010/2011-revised-table-14.zip), [2015](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2015/table142015revised.zip), [2020](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2020revised/table142020revised.zip), [2022](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2022revised/ashetable142022revised.zip), [2025](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2025provisional/ashetable142025provisional.zip)
10. [ABS: Labour Force, Australia, Detailed, table EQ08 (Employed persons by Occupation unit group, ANZSCO 2013), latest release](https://www.abs.gov.au/statistics/labour/employment-and-unemployment/labour-force-australia-detailed/latest-release), Australian Bureau of Statistics

### Wage series

11. [University of Missouri Libraries — Prices and Wages by Decade: 1960-1969 (BLS construction industry wage context)](https://libraryguides.missouri.edu/pricesandwages/1960-1969), University of Missouri Libraries / BLS historical sources
12. [FRED / BLS — Average Hourly Earnings of All Employees, Construction (CES2000000003), 1980 data](https://fred.stlouisfed.org/series/CES2000000003), Federal Reserve Bank of St. Louis / Bureau of Labor Statistics
13. [BLS OES 2000 national estimates (flat file)](https://www.bls.gov/oes/special-requests/oes00nat.zip), Bureau of Labor Statistics
14. 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), [2025](https://www.bls.gov/oes/special-requests/oesm25nat.zip)
15. [BLS Occupational Outlook Handbook — Construction Managers, median annual wage May 2024: $106,980](https://www.bls.gov/ooh/management/construction-managers.htm), Bureau of Labor Statistics
16. [Statistics Canada, Census of Population 2006, Table 97-563-XCB2006069 (Wage and salary statistics by occupation, NOC-S 2006), income reference year 2005](https://www12.statcan.gc.ca/census-recensement/2006/dp-pd/tbt/Rp-eng.cfm?LANG=E&PID=96285), Statistics Canada
17. [Statistics Canada, Census of Population 2016, Table 98-400-X2016356 (Occupation by employment income statistics, NOC 2016), income reference year 2015](https://www150.statcan.gc.ca/n1/en/catalogue/98-400-X2016356), Statistics Canada
18. [Statistics Canada, Census of Population 2021, Table 98-10-0586 (Employment income statistics by occupation unit group, NOC 2021), income reference year 2020](https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=9810058601), Statistics Canada
19. ONS: Annual Survey of Hours and Earnings, Table 14.7a (Annual pay - Gross), 4-digit SOC 1122, United Kingdom. Office for National Statistics, Annual Survey of Hours and Earnings, Table 14. Licensed under the Open Government Licence v3.0., Office for National Statistics. Editions: [2002](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2002/2002-table-14.zip), [2006](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2006consistentw_007methodology/2006-table-14.zip), [2010](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2010revised/2010-revised-table-14.zip), [2011](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2011revisedbasedonsoc2010/2011-revised-table-14.zip), [2015](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2015/table142015revised.zip), [2020](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2020revised/table142020revised.zip), [2022](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2022revised/ashetable142022revised.zip), [2025](https://www.ons.gov.uk/file?uri=/employmentandlabourmarket/peopleinwork/earningsandworkinghours/datasets/occupation4digitsoc2010ashetable14/2025provisional/ashetable142025provisional.zip)
20. [Jobs and Skills Australia: Construction Managers (ABS Survey of Employee Earnings and Hours, May 2025)](https://www.jobsandskills.gov.au/data/occupation-and-industry-profiles/occupations/1331-construction-managers), Jobs and Skills Australia / Australian Bureau of Statistics

### Tool eras

21. [Norcross Brothers — Wikipedia (firm operations 1864-1910, integrated materials and management model)](https://en.wikipedia.org/wiki/Norcross_Brothers), Wikipedia
22. [History of Construction Management — Smoky Hill Engineering (scientific management and Gantt chart adoption in construction)](https://smokyhilleng.com/history-of-construction-management/), Smoky Hill Engineering
23. [Florida Consultants — "A Brief History of CPM Scheduling in Construction" (CPM origins 1957-58, DuPont/Remington Rand)](https://www.florida-consultants.com/post/a-brief-history-of-cpm-scheduling-in-construction), Florida Consultants
24. [Construction Management Association of America — Wikipedia (CMAA founded 1982, agency CM model)](https://en.wikipedia.org/wiki/Construction_Management_Association_of_America), Wikipedia / CMAA
25. [Wikipedia — Building information modeling (BIM history, Autodesk Revit acquisition 2002, development timeline)](https://en.wikipedia.org/wiki/Building_information_modeling), Wikipedia
26. [McKinsey Global Institute — The Next Normal in Construction (2020): productivity, digitization, and technology adoption statistics](https://www.mckinsey.com/capabilities/operations/our-insights/the-next-normal-in-construction-how-disruption-is-reshaping-the-worlds-largest-ecosystem), McKinsey Global Institute
27. [ENR — AI Tools Transform Construction Project Management (2025): Procore adoption, construction technology landscape](https://www.enr.com/articles/58903-ai-tools-transform-construction-project-management), Engineering News-Record
28. [Procore — Advances Future of Construction with AI Innovations at Groundbreak 2025 (18+ AI agents; RFI and submittal automation)](https://www.procore.com/press/procore-advances-the-future-of-construction-with-new-ai-innovations), Procore Technologies
29. [OpenSpace — Visual Intelligence Platform Launch (Sep 2025): 62% of ENR Top 400 adopted](https://www.openspace.ai/press-releases/visual-intelligence-platform/), OpenSpace AI

### Forecasts and exposure studies

30. [BLS Employment Projections 2025-35, National Employment Matrix: 11-9021 Construction managers (2025: 609.1 thousand; 2035: 664.3 thousand; +9.1%)](https://data.bls.gov/projections/nationalMatrix?queryParams=11-9021&ioType=o), Bureau of Labor Statistics
31. [Eloundou, Manning, Mishkin & Rock (2023), "GPTs are GPTs", occupation-level exposure data occ\_level.csv (O\*NET-SOC 11-9021.00, human-rated β 0.4)](https://github.com/openai/GPTs-are-GPTs/blob/main/data/occ_level.csv), OpenAI

### Historical notes

32. [Norcross Brothers — Wikipedia (Trinity Church, Boston 1872-1877; foundation engineering by Orlando Norcross)](https://en.wikipedia.org/wiki/Norcross_Brothers), Wikipedia
33. [History of Construction Management — Smoky Hill Engineering (Taylor, Gantt, scientific management adoption in construction)](https://smokyhilleng.com/history-of-construction-management/), Smoky Hill Engineering
34. [Florida Consultants — "A Brief History of CPM Scheduling in Construction" (CPM/PERT origins 1957-58)](https://www.florida-consultants.com/post/a-brief-history-of-cpm-scheduling-in-construction), Florida Consultants
35. [Construction Management Association of America — Wikipedia (CMAA founded 1982; CCM credential 1993; ISO accreditation 2006)](https://en.wikipedia.org/wiki/Construction_Management_Association_of_America), Wikipedia / CMAA
36. [BLS Occupational Outlook Handbook — Construction Managers (IIJA and infrastructure investment as growth driver, 2024-2034 projections)](https://www.bls.gov/ooh/management/construction-managers.htm), Bureau of Labor Statistics
37. [Procore — Advances Future of Construction with AI Innovations at Groundbreak 2025](https://www.procore.com/press/procore-advances-the-future-of-construction-with-new-ai-innovations), Procore Technologies

### Predecessors & successors

38. [Norcross Brothers — Wikipedia (firm structure: trade foremen as predecessors to the general contractor model)](https://en.wikipedia.org/wiki/Norcross_Brothers), Wikipedia

### Present-day analysis

- [O\*NET 30.3 — Construction Managers (11-9021.00)](https://www.onetonline.org/link/summary/11-9021.00), accessed 2026-05-24
- [BLS Occupational Outlook Handbook — Construction Managers (2024–2034)](https://www.bls.gov/ooh/management/construction-managers.htm), accessed 2026-05-24
- [Eloundou et al. 2024 — GPTs are GPTs (Science)](https://arxiv.org/abs/2303.10130), accessed 2026-05-24
- [ABC — Construction Workforce Shortage Tops 500,000 in 2026](https://www.abc.org/News-Media/News-Releases/entryid/19362/abc-construction-workforce-shortage-tops-500-000-in-2026), accessed 2026-05-24
- [Procore — Advances Future of Construction with AI Innovations at Groundbreak 2025](https://www.procore.com/press/procore-advances-the-future-of-construction-with-new-ai-innovations), accessed 2026-05-24
- [OpenSpace — Visual Intelligence Platform Launch (Sep 2025): 62% of ENR Top 400 adopted](https://www.openspace.ai/press-releases/visual-intelligence-platform/), accessed 2026-05-24
- [ALICE Technologies — Generative Schedule Optimization for Construction](https://www.alicetechnologies.com/), accessed 2026-05-24
- [ENR — AI Tools Transform Construction Project Management (2025)](https://www.enr.com/articles/58903-ai-tools-transform-construction-project-management), accessed 2026-05-24
- [McKinsey Global Institute — The Next Normal in Construction (2020, updated 2024)](https://www.mckinsey.com/capabilities/operations/our-insights/the-next-normal-in-construction), accessed 2026-05-24
- [Document Crunch — AI Contract Review for Construction (2025)](https://www.documentcrunch.com/), accessed 2026-05-24
- [viAct — AI Construction Safety Monitoring: PPE Detection and Hazard Alerts (2025)](https://www.viact.ai/), accessed 2026-06-22
- [Togal.AI — Automated Construction Takeoff (2025)](https://www.togal.ai/), accessed 2026-05-24
- [DroneDeploy — AI-Powered Drone Mapping and Site Intelligence for Construction (2025)](https://www.dronedeploy.com/solutions/construction/), accessed 2026-06-22
- [Buildots — AI Construction Progress Tracking (2025)](https://buildots.com/), accessed 2026-05-24
- [Autodesk Construction Cloud — Construction IQ, AutoSpecs AI, Symbol Detection AI features](https://construction.autodesk.com/resources/artificial-intelligence/), accessed 2026-05-24

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