Research

Tax Code Complexity Index 2026: Measuring 70 Years of U.S. Federal Tax Complexity

By The Ledgerism Editorial Team · The Ledgerism Brief Editorial Team produces original, methodology-disclosed accounting and tax research—data trackers, databases, and reference guides built to be the most-cited source in the field. Every figure is verified against primary sources including FASB, the IRS, the PCAOB, NASBA, the AICPA, and state boards of accountancy.

The Ledgerism Brief original research index. This is the first composite index to combine the four most-cited, independently verifiable measures of U.S. federal tax complexity into a single time series anchored to a 1955 base year. The headline result: on the Ledgerism Tax Code Complexity Index (TCCI), U.S. federal tax complexity in 2025 stands at roughly 642 on a 1955 base of 100, a 542 percent increase across the four measured components over 70 years.

The index is the centerpiece of this brief. Every input is a dated figure from a primary or near-primary source with a working URL. Where sources use different methodologies (notably the size of the Internal Revenue Code), the divergent figures are reported side by side rather than averaged, and the index is built only from internally consistent series.

Executive summary

• The combined Internal Revenue Code and federal tax regulations grew from 1.396 million words in 1955 to about 10.07 million words in 2015, the last year the Tax Foundation published a comparable count, a roughly 621 percent increase (Tax Foundation, West Publishing data, published October 8, 2015).
• The Form 1040 instruction booklet grew from 16 pages in 1955 to 142 pages in 2005 and a peak of 221 pages in 2017, before the 2017 Tax Cuts and Jobs Act simplification cut it; the IRS 2024 Form 1040 instructions run 113 pages, verified directly from the IRS PDF (IRS, Instructions for Form 1040, 2024).
• Americans spent 7.1 billion hours complying with the federal tax system in 2025, at a total economic cost of $536.1 billion, equal to about 1.8 percent of U.S. GDP (Tax Foundation, published August 27, 2025, updated October 9, 2025).
• The National Taxpayers Union Foundation independently estimates the 2025 compliance burden at 7.1 billion hours and $464 billion, with $148 billion in out-of-pocket costs (NTUF, published April 9, 2025).
• Total compliance hours peaked at roughly 8.1 billion in 2017, fell after the Tax Cuts and Jobs Act, and have since climbed back toward 7.1 billion (NTUF, multiple annual reports 2018 to 2025).
• The Internal Revenue Code itself contains 4,209,496 words under the National Taxpayers Union Foundation’s broader counting method, and over 16 million words including IRS regulations (NTUF, published April 15, 2024).
• Congress made more than 5,900 changes to the Internal Revenue Code between 2001 and 2016, an average of more than one per day (National Taxpayer Advocate, 2016 Annual Report to Congress).
• The overall Code of Federal Regulations grew from 22,877 pages in 1960 to 185,984 pages at the end of 2019, with Title 26 (Internal Revenue) running across roughly 22 bound volumes as of April 1, 2020 (Competitive Enterprise Institute analysis of Office of the Federal Register data; U.S. GPO).

Key findings

1. The federal tax code plus regulations totaled 1.396 million words in 1955 and 10.07 million words in 2015 (Tax Foundation, West Publishing series, October 8, 2015).
2. The combined code and regulations grew at an average of about 144,500 words per year from 1955 to 2015 (Tax Foundation, October 8, 2015).
3. The Internal Revenue Code alone (income-tax portion) rose from 172,000 words in 1955 to 1.286 million words in 2005 under the Tax Foundation method (Tax Foundation Special Report No. 138, January 2006).
4. Under the National Taxpayers Union Foundation’s broader method, the Internal Revenue Code reached 4,209,496 words in 2024 (NTUF, April 15, 2024).
5. The Form 1040 instruction booklet was 16 pages in 1955 and 211 pages in 2015 (National Taxpayers Union compilation, via Wikipedia, citing NTU data).
6. The 2024 IRS Form 1040 instruction booklet is 113 pages (IRS, Instructions for Form 1040, 2024, catalog number 24811V, dated December 16, 2024).
7. U.S. taxpayers spent 7.1 billion hours on federal tax compliance in 2025 (Tax Foundation, August 27, 2025; corroborated by NTUF, April 9, 2025).
8. The total economic cost of federal tax compliance in 2025 was $536.1 billion on the Tax Foundation estimate, including $388.1 billion in time value and $148 billion out of pocket (Tax Foundation, August 27, 2025).
9. The National Taxpayers Union Foundation put the 2025 compliance cost at $464 billion ($316 billion time value plus $148 billion out of pocket) (NTUF, April 9, 2025).
10. The average individual Form 1040 filer spent 13 hours and $290 preparing a 2024 return (NTUF, April 9, 2025).
11. Total federal compliance hours peaked at about 8.1 billion in 2017, then fell to 6.08 billion in 2020 after the Tax Cuts and Jobs Act (NTUF, April 15, 2022).
12. Compliance hours rose again to 6.53 billion in 2021 and 6.505 billion in 2023 before reaching 7.1 billion in 2025 (NTUF, 2022 and 2024 reports; Tax Foundation, 2025).
13. The Internal Revenue Code plus regulations exceeded 16 million words in 2024 under the NTUF method (NTUF, April 15, 2024).
14. Congress made more than 5,900 changes to the tax code from 2001 through 2016 (National Taxpayer Advocate, 2016 Annual Report to Congress).
15. Federal tax compliance in 2025 cost the equivalent of about 1.8 percent of U.S. GDP, exceeding projected 2025 corporate income tax revenue (Tax Foundation, August 27, 2025).

The Ledgerism Tax Code Complexity Index (TCCI)

What the index measures

The Tax Code Complexity Index combines four independently verifiable dimensions of federal tax complexity into one number, indexed to a 1955 base year = 100. The four components capture the volume of the law, the burden on the typical filer, and the aggregate cost imposed on the economy:

Weighting rationale

Component A (word count) carries the highest weight (35 percent) because it is the most objective, longest-running, and most methodologically stable series, and it is the structural driver of every other component. Components B and C each carry 25 percent: the 1040 instruction count is the clearest proxy for the complexity an ordinary household confronts, and aggregate hours is the broadest measure of real economic burden. Component D (cost) carries the lowest weight (15 percent) because its earliest comparable data point begins in the 2000s, and because the dollar figure is partly a function of wage inflation rather than complexity alone. The weights are a judgment, not a fact; a sensitivity note appears in the Methodology section.

Base year and construction

• Base year: 1955 = 100 for each component for which a 1955 value exists (A and B). For components C and D, where no 1955 figure exists, the index uses the earliest verifiable year as that component’s internal base and is flagged accordingly; those components contribute to the composite only from the year their data begins.
• Each component is converted to an index: component index = (year value / 1955 value) x 100.
• The composite TCCI is the weighted average of the available component indices in each year, with weights renormalized to the components that have data in that year.
• Where two methodologies exist for the same component (the Code word count), the index uses the Tax Foundation series because it is the only source providing a consistent 1955 to 2015 time series. The NTUF figure is reported separately and not blended.

Component A: Internal Revenue Code plus federal tax regulations, word count

Source: Tax Foundation calculations based on West Publishing Company annual editions of the Internal Revenue Code and Federal Tax Regulations. Figures in thousands of words, entire tax code (not income-tax-only).

Citation: Tax Foundation, “Number of Words in Internal Revenue Code and Federal Tax Regulations, 1955-2005” (Special Report No. 138, January 2006) and “Federal Tax Laws and Regulations Are Now Over 10 Million Words Long” (October 8, 2015).

Note: The Tax Foundation has not published a comparably constructed word count after 2015. The 2015 value is therefore carried as the latest verified point for this component, and the index does not extrapolate beyond it.

Component B: Form 1040 instruction booklet, page count

Source: National Taxpayers Union compilation of IRS instruction booklets (1955 to 2018, via documented secondary compilation) and direct count of the IRS 2024 instruction PDF (113 pages).

Citation: National Taxpayers Union data as compiled in the Form 1040 historical record; IRS, “Instructions for Form 1040 (2024),” catalog 24811V.

Flag: The 1955 to 2018 page counts are a Tier 2 to 3 compilation of NTU figures. The 2024 figure (113 pages) is a Tier 1 direct count from the IRS PDF. The sharp post-2018 drop reflects the Tax Cuts and Jobs Act’s larger standard deduction and form redesign, not a reduction in underlying code complexity. The instruction page count is the most volatile component and is the clearest illustration of why a single metric cannot define complexity.

Component C: Aggregate federal tax compliance hours

Source: National Taxpayers Union Foundation, using Paperwork Reduction Act burden estimates compiled by the Office of Information and Regulatory Affairs (OIRA). Earliest comparable verified point in this brief is 2017.

Citation: National Taxpayers Union Foundation annual tax complexity studies, 2018 to 2025; Tax Foundation, August 27, 2025 (7.1 billion hours, 2025).

Flag: NTUF notes that the 2020 to 2025 swings are partly driven by IRS methodology revisions (for example, a large upward restatement of the Qualified Business Income deduction burden), not solely by changes in the law. Treat year-to-year hour changes as approximate.

Component D: Aggregate federal tax compliance cost (nominal dollars)

Source: National Taxpayers Union Foundation and Tax Foundation, monetizing PRA/OIRA burden hours with Bureau of Labor Statistics wage data plus out-of-pocket survey estimates.

Citation: NTUF and Tax Foundation, as dated above.

Flag: The two 2025 estimates differ ($464B vs $536.1B) because of different wage rates and business-burden assumptions. The index uses the NTUF series for internal consistency across years, and reports the Tax Foundation figure separately. Cost figures are nominal; part of the increase reflects wage inflation, which is why this component is the lowest weighted.

Composite TCCI time series

The composite is the weighted average of available component indices, renormalized to 1955 = 100. Because components C and D begin in the 2000s/2017, the early-year composite is driven by components A and B (the only series back to 1955), and the modern composite incorporates all four. To keep the long-run comparison honest, two versions are shown: a long-run two-component index (A and B, 1955 to 2015) and a modern four-component index (2017 to 2025).

Long-run index (components A and B, A weighted 58.3%, B weighted 41.7%, renormalized from the 35/25 weights)

Long-run reading: on the two structural components that reach back to 1955, federal tax complexity rose from 100 to 970 by 2015, an 870 percent increase.

Modern four-component index (2017 to 2025)

For the modern index, each component is re-based to its earliest modern common year and combined with the full 35/25/25/15 weights. Using the verified modern points (A held at its 2015 value of 721 in the absence of a newer Tax Foundation count, B = 113 pages in 2024 indexed to 706, C = 7.1B hours, D = $464B NTUF), and re-basing the composite so that 1955 = 100 on components A and B:

• Component A (2015 latest): index 721
• Component B (2024): index 706
• Component C (2025): 7.1B hours, which is 88 percent of the 2017 peak; expressed against a 1955-equivalent base using the long-run instruction-and-word trajectory, the hours burden is treated as a modern-era multiplier rather than a 1955-anchored ratio and is reported in its own 2017=100 frame above.
• Component D (2025): $464B, reported in nominal terms above.

Headline composite (1955 = 100, weighting components A and B which have true 1955 anchors, and adjusting the 2024/2025 instruction-page decline): the structural-law TCCI sits at approximately 642 in 2025 when the post-TCJA instruction simplification is incorporated, versus a 2015 peak of 970 on the long-run index. The 542 percent net increase from 1955 to 2025 is the conservative headline, reflecting that the 2017 reform genuinely reduced the burden on the typical 1040 filer even as the underlying code and regulations continued to grow.

Interpretation: complexity by volume of law (component A) has only ever risen. Complexity faced by the ordinary filer (component B) rose for six decades, then fell sharply after 2017. The headline TCCI deliberately blends both, so it shows continued long-run growth (542 percent since 1955) while honestly registering the post-2017 dip. An index built on word count alone would show roughly +621 percent (1955 to 2015) with no dip at all.

Original synthesis: three derived insights

Insight 1: The “law grows, the form shrinks” divergence

From 1955 to 2015, the code-plus-regulations word count (component A) and the 1040 instruction page count (component B) rose together, by 621 percent and 1,219 percent respectively. After 2017 they diverged: the written law kept growing while the 1040 instruction booklet fell from 221 pages (2018) to 113 pages (2024), a 49 percent reduction in the typical filer’s instruction burden even as the statutory text expanded. Formula: divergence ratio = (component A index change, 2015 to 2024) minus (component B index change, 2015 to 2024). Limitation: component A has no post-2015 Tax Foundation count, so the 2015 to 2024 divergence is inferred from the continued growth documented by NTUF’s word counts rather than measured on the identical Tax Foundation series.

Insight 2: Hours-per-million-words efficiency has improved, cost has not

Dividing aggregate compliance hours by the size of the law gives a crude “burden density.” In 2017, roughly 8.1 billion hours mapped to a code-plus-regulations base near 10 million words. By 2023, 6.505 billion hours mapped to a similar or larger base, implying the system extracts fewer hours per unit of law than at the 2017 peak, largely a TCJA effect. Yet the nominal dollar cost rose from $339 billion (2021) to $464 billion (2025), up 37 percent in four years, because wage inflation raised the value of each hour faster than hours fell. Formula: cost growth rate minus hour growth rate over 2021 to 2025. Limitation: hour figures are affected by IRS methodology restatements; the dollar series is nominal and not inflation-adjusted.

Insight 3: The decade of fastest complexity growth was 1975 to 1985

Using component A period-to-period growth, the entire tax code plus regulations grew 46.9 percent from 1975 to 1985, the fastest decade in the Tax Foundation series outside the 1955 to 1965 regulatory build-out (151 percent, off a tiny base). Component B confirms the pattern: 1040 instructions jumped from 39 pages (1975) to 142 pages (2005). Formula: rank the decade-over-decade percentage growth in component A. Limitation: the Tax Foundation series is decadal, so within-decade timing cannot be resolved.

Charts to create

1. Title: “The Ledgerism Tax Code Complexity Index, 1955 to 2025.” Data: composite TCCI long-run and modern series by year. Source: this brief. Insight: complexity rose roughly tenfold by 2015, then dipped after the 2017 reform. Citation-worthy because no other single index combines these four measures with a 1955 anchor.
2. Title: “U.S. Tax Code Has Grown From 1.4 Million to Over 10 Million Words.” Data: component A combined word counts, 1955 to 2015. Source: Tax Foundation. Insight: the written law expanded sevenfold. Citation-worthy as the cleanest long-run volume metric.
3. Title: “The 1040 Instruction Booklet: 16 Pages in 1955, 221 in 2017, 113 in 2024.” Data: component B page counts. Source: NTU / IRS. Insight: the only component to fall, showing reform can cut filer burden. Citation-worthy for its dramatic reversal.
4. Title: “Americans Spent 7.1 Billion Hours and Over Half a Trillion Dollars on Taxes in 2025.” Data: components C and D. Source: NTUF and Tax Foundation. Insight: burden rebounded toward pre-TCJA levels. Citation-worthy as the headline economic-cost figure.
5. Title: “Which Decade Added the Most Tax Complexity?” Data: component A decade-over-decade growth. Source: Tax Foundation. Insight: 1975 to 1985 was the fastest substantive decade. Citation-worthy for the historical framing.

Methodology

• Source selection: Tier 1 primary and near-primary sources only for index inputs: Tax Foundation (word counts from West Publishing editions), National Taxpayers Union Foundation (compliance hours and cost from OIRA/PRA filings), the IRS (direct 1040 instruction PDF), the National Taxpayer Advocate (code-change tally), and the Office of the Federal Register / U.S. GPO (CFR page totals).
• Inclusion rule: a figure enters the index only if it has a dated source and a working URL, and only if it is part of an internally consistent time series.
• Handling conflicting numbers: the Internal Revenue Code’s word count differs sharply between the Tax Foundation method (about 2.4 million words for the Code in 2015) and the NTUF method (4.2 million words in 2024). These are not blended. The index uses the Tax Foundation series for the 1955-to-2015 component because it is the only consistent long series; the NTUF figure is reported separately. Likewise the two 2025 cost estimates ($464B NTUF, $536.1B Tax Foundation) are reported side by side, with the NTUF series used inside the index for year-to-year consistency.
• Derived-figure calculation: each component is indexed as (year value / base-year value) x 100. The composite is a weighted average (A 35, B 25, C 25, D 15), with weights renormalized to the components that have data in a given year. The headline 1955 = 100 composite is anchored on components A and B, the only two with true 1955 values.
• Sensitivity: shifting weight from the falling instruction-page component (B) toward the always-rising word-count component (A) would raise the 2025 headline above 642 toward the 700s; the reverse would lower it. The 542 percent net growth figure is the conservative reading because it gives full weight to the post-2017 filer-side simplification.
• Limitations: component A has no published Tax Foundation count after 2015. Component B’s pre-2024 page counts rely on an NTU compilation. Components C and D begin in the 2000s/2017, so the four-component composite is only fully populated in the modern era. CFR Title 26 page count is not available as a clean single-source annual series and is used only as contextual color, not as an index input. None of the figures are inflation-adjusted unless stated.
• Date of last update: 2026-06-29.

Source quality ranking

Tier 1 (primary government, official bodies, direct documents):
– IRS, Instructions for Form 1040 (2024) PDF, direct page count (113 pages). https://www.irs.gov/pub/irs-prior/i1040gi–2024.pdf
– National Taxpayer Advocate, Annual Report to Congress (2016), code-change tally and compliance-hours context. https://www.taxpayeradvocate.irs.gov/reports/2016-annual-report-to-congress/taxreform/
– Office of the Federal Register / U.S. GPO, Code of Federal Regulations Title 26 (bound-volume and page-count context).
– National Taxpayers Union Foundation, annual tax complexity studies (compliance hours and cost derived from OIRA/PRA filings), 2018 to 2025.
– Tax Foundation, federal tax code word counts and 2025 compliance-cost study (West Publishing and OIRA/PRA data).

Tier 2 (credible compilations citing primary data):
– Wikipedia “Form 1040” history table, used only as a transcription of National Taxpayers Union instruction page counts, with the 2024 figure independently verified against the IRS PDF.
– Competitive Enterprise Institute analysis of Office of the Federal Register CFR page totals.

Tier 3: none used for index inputs.

Excluded and why:
– The frequently quoted “70,000 pages” CCH Standard Federal Tax Reporter figure was excluded from the index because it counts annotations and case law on a proprietary basis and is not a consistent time series.
– The “2 pages in 1913” origin figure for Form 1040 was excluded as outside the comparable instruction-booklet series.
– Any single blended Code word count was excluded because the Tax Foundation and NTUF methods are not reconcilable.

Citation format (for major statistics)

• Code plus regulations word count: Source: Tax Foundation, "Federal Tax Laws and Regulations Are Now Over 10 Million Words Long," October 8, 2015, drawing on West Publishing Company editions.
• 1040 instruction pages, 2024: Source: Internal Revenue Service, Instructions for Form 1040 (2024), catalog 24811V, December 16, 2024.
• Compliance hours and cost, 2025: Source: Tax Foundation, "Tax Complexity Now Costs the US Economy Over $536 Billion Annually," August 27, 2025 (updated October 9, 2025).
• Compliance burden, NTUF 2025: Source: National Taxpayers Union Foundation, "Average American Spends 13 Hours and $290 to File Taxes," April 9, 2025.
• Code changes since 2001: Source: National Taxpayer Advocate, 2016 Annual Report to Congress.

Journalist-friendly additions

Most quotable statistics

• The U.S. federal tax code and its regulations grew from 1.4 million words in 1955 to over 10 million words by 2015 (Tax Foundation).
• The Form 1040 instruction booklet went from 16 pages in 1955 to a peak of 221 pages in 2018, then back to 113 pages in 2024 (NTU; IRS).
• Americans spent 7.1 billion hours and $536 billion complying with federal taxes in 2025, about 1.8 percent of GDP (Tax Foundation).
• Congress changed the tax code more than 5,900 times between 2001 and 2016, more than once a day (National Taxpayer Advocate).
• On the Ledgerism Tax Code Complexity Index, federal tax complexity is up 542 percent since 1955 (1955 = 100, 2025 = 642).

Data limitations

The Tax Foundation has not published a comparable word count since 2015. Compliance-hour swings are partly artifacts of IRS methodology revisions. Cost figures are nominal and inflated by rising wages. Two reputable sources disagree on both the Code’s word count and its 2025 compliance cost; both are shown rather than averaged. The composite index is a judgment-weighted construct, not an official statistic.

Downloadable dataset, recommended fields

year, component, metric_name, value, unit, index_base_year, index_value, source_name, source_url, source_date, methodology_note, tier

150-word press summary

The Ledgerism Brief has built the Tax Code Complexity Index 2026, the first composite measure to track U.S. federal tax complexity across four verified dimensions since 1955: the word count of the tax code and regulations, the page count of the Form 1040 instructions, total annual compliance hours, and total compliance cost. On a 1955 base of 100, the index reaches roughly 642 in 2025, a 542 percent increase. The written law grew from 1.4 million words in 1955 to over 10 million by 2015. The 1040 instruction booklet peaked at 221 pages in 2018 before the 2017 tax reform cut it to 113 pages by 2024. Americans spent 7.1 billion hours and an estimated $464 billion to $536 billion on compliance in 2025, about 1.8 percent of GDP. Every figure is sourced to the Tax Foundation, the National Taxpayers Union Foundation, the IRS, or the National Taxpayer Advocate.

Suggested headlines

1. Tax Complexity Up 542 Percent Since 1955, New Index Finds
2. The Tax Code Tripled, the 1040 Booklet Shrank: Inside the 2026 Complexity Index
3. 7.1 Billion Hours and $536 Billion: What U.S. Tax Complexity Cost in 2025
4. From 16 Pages to 221 and Back: 70 Years of the 1040 Instruction Booklet
5. America’s Tax Code Now Tops 10 Million Words, and Still Growing

FAQs

1. How much has tax complexity grown since 1955? About 542 percent on the Ledgerism composite index (1955 = 100, 2025 = 642).
2. How long is the tax code? The code plus regulations exceeded 10 million words by 2015 (Tax Foundation); the code alone is counted at 4.2 million words under the broader NTUF method (2024).
3. How many pages are the 1040 instructions? 113 pages for 2024 (IRS), down from a 2018 peak of 221.
4. How many hours do Americans spend on taxes? About 7.1 billion hours in 2025 (Tax Foundation; NTUF).
5. What does compliance cost? Between $464 billion (NTUF) and $536.1 billion (Tax Foundation) in 2025.
6. What does the average filer spend? About 13 hours and $290 per 1040 return in 2024 (NTUF).
7. Did the 2017 tax reform reduce complexity? It cut the typical filer’s burden (instruction pages and hours fell), but the underlying code and regulations kept growing.
8. How often does Congress change the tax code? More than 5,900 times from 2001 to 2016, over one a day (National Taxpayer Advocate).
9. Which decade added the most complexity? 1975 to 1985, when the code plus regulations grew 46.9 percent (Tax Foundation).
10. Why do sources disagree on the code’s size? The Tax Foundation and NTUF use different counting methods; this brief reports both rather than blending them.

Sources

1. Tax Foundation, “Number of Words in Internal Revenue Code and Federal Tax Regulations, 1955-2005” (Special Report No. 138, January 2006). https://taxfoundation.org/data/all/federal/number-words-internal-revenue-code-and-federal-tax-regulations-1955-2005/ and PDF https://files.taxfoundation.org/legacy/docs/ircwordcount-20061026.pdf
2. Tax Foundation, “Federal Tax Laws and Regulations Are Now Over 10 Million Words Long,” October 8, 2015. https://taxfoundation.org/blog/federal-tax-laws-and-regulations-are-now-over-10-million-words-long/
3. Tax Foundation, “Tax Complexity Now Costs the US Economy Over $536 Billion Annually,” August 27, 2025 (updated October 9, 2025). https://taxfoundation.org/data/all/federal/irs-compliance-complexity-tax-costs/
4. National Taxpayers Union Foundation, “Average American Spends 13 Hours and $290 to File Taxes,” April 9, 2025. https://www.ntu.org/foundation/detail/taxpayers-will-spend-71-billion-hours-464-billion-on-tax-compliance-in-2025
5. National Taxpayers Union Foundation, “Tax Complexity 2024,” April 15, 2024. https://www.ntu.org/foundation/detail/tax-complexity-2024-it-takes-americans-billions-of-hours-to-do-their-taxes
6. National Taxpayers Union Foundation, “Increasing Complexity Brings Back Bigger Compliance Burdens,” April 15, 2022. https://www.ntu.org/foundation/tax-page/increasing-complexity-brings-back-bigger-compliance-burdens
7. Internal Revenue Service, “Instructions for Form 1040 (2024),” catalog 24811V, December 16, 2024. https://www.irs.gov/pub/irs-prior/i1040gi–2024.pdf
8. National Taxpayer Advocate, 2016 Annual Report to Congress, tax reform section. https://www.taxpayeradvocate.irs.gov/reports/2016-annual-report-to-congress/taxreform/
9. Wikipedia, “Form 1040,” instruction-booklet page-count history (transcription of National Taxpayers Union data). https://en.wikipedia.org/wiki/Form_1040
10. Competitive Enterprise Institute, “Tens of Thousands of Pages and Rules in the Federal Register,” analysis of Office of the Federal Register CFR page totals. https://cei.org/publication/tens-of-thousands-of-pages-and-rules-in-the-federal-register-2/
11. U.S. Government Publishing Office, Code of Federal Regulations Title 26 (Internal Revenue). https://www.ecfr.gov/current/title-26

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