VivMetric Data Sources: CDC, WHO, NIH, USDA, NSF Citations

Per-Source Deep Dive 1: Centers for Disease Control and Prevention (cdc.gov)

The US Centers for Disease Control and Prevention (CDC), headquartered in Atlanta, Georgia, is an agency within the US Department of Health and Human Services (HHS). Three specific CDC publications form the reference inputs for adult BMI classification, pediatric BMI-for-age growth charts, and population BMI distribution statistics used across VivMetric calculator outputs and reference pages.

Adult BMI Classifications — 2024 Review Date

Document identifier: "BMI for Children and Teens" — Atlanta, GA: US Department of Health and Human Services; Centers for Disease Control and Prevention; National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP); Division of Nutrition, Physical Activity, and Obesity (DNPAO). Last content reviewed January 10, 2024. Internal CDC document tracking identifier: CDC-DPH-2024-0003. This page defines the standard adult BMI four-category classification used on the [Adult BMI Calculator](../tools/bmi-calculator.html): BMI below 18.5 = Underweight range, BMI 18.5 through 24.9 = Healthy Weight range, BMI 25.0 through 29.9 = Overweight range, BMI 30.0 and above = Obesity range. The same document explicitly states: "BMI is a screening tool. It does not diagnose body fatness or health." This disclaimer is reproduced verbatim on every BMI-related calculator page and in the body composition articles.

2000 Pediatric BMI-for-Age Growth Charts — NCHS Vital Health Stat 11(246)

Full citation: Kuczmarski RJ, Ogden CL, Guo SS, Grummer-Strawn LM, Flegal KM, Mei Z, Wei R, Curtin LR, Roche AF, Johnson CL. "CDC Growth Charts: United States." Vital Health Statistics Series 11, Number 246. Hyattsville, MD: National Center for Health Statistics (NCHS), part of CDC. May 2000. DHHS Publication No. (PHS) 2000-1696. Length: 58 pages, 30 tables, 6 full-color chart plates. Sample: n=27,940 US children and adolescents aged 2-19 years consolidated from NHES I, NHES II, NHES III, NHANES I, NHANES II national surveys. Methodology: LMS Box-Cox smoothing per Cole 1990. Used as the percentile lookup reference for the [Teen BMI Calculator](../tools/bmi-teen-calculator.html). Companion clinical guide: "Using and Interpreting the CDC Growth Charts." MMWR Recommendations and Reports, 2002; 51(RR-12): 1-15. Published October 18, 2002.

NHANES 2017–March 2020 BMI Population Prevalence

Full citation: Fryar CD, Carroll MD, Ogden CL. "Prevalence of Overweight, Obesity, and Severe Obesity Among Adults Aged 20 and Over: United States, 2017–March 2020." NCHS Data Brief No. 409. Hyattsville, MD: National Center for Health Statistics. Published February 2022. This document provides the survey-weighted population percentages used in the [Height-to-Weight Reference Ranges](../articles/standard-weight-ranges.html) article: 41.9% obese, 30.7% overweight, 18.2% normal, 9.2% underweight. All four sub-tables (age, sex, race and Hispanic origin, income-to-poverty ratio) are available as downloadable XLSX files from the NCHS public data portal.

Per-Source Deep Dive 2: World Health Organization (who.int)

The World Health Organization (WHO) is a specialized agency of the United Nations headquartered in Geneva, Switzerland, with six regional offices (AFRO, AMRO, EMRO, EURO, SEARO, WPRO) and 194 Member States. Three WHO publications or databases form reference inputs for VivMetric formulas and category ranges.

WHO Global Database on Body Mass Index — Annual NCD Country Profiles Release

Database URL: who.int/ncds/country-profiles. Maintained by the Noncommunicable Diseases and Mental Health Cluster (NMH Cluster), Surveillance, Implementation, and Economics Unit. Updated annually. Standard methodology: direct age-standardization using the WHO Standard Population for all country summaries. Data originates from nationally representative population health examination surveys in each Member State, with measured BMI used when available and self-reported BMI adjusted by regression coefficients when measured surveys are unavailable. 2023 release estimates: 1.1 billion adults globally classified at BMI ≥30.0, 763 million at BMI 25.0-29.9. Used for the country-mean BMI comparison table in the [Standard Weight Ranges](../articles/standard-weight-ranges.html) article.

WHO 2000 Obesity Report — Technical Report Series 894, ISBN 9241591714

Full citation: World Health Organization. "Obesity: Preventing and Managing the Global Epidemic." Report of a WHO Consultation on Obesity, Geneva, 3-5 June 1997. WHO Technical Report Series 894. Geneva: World Health Organization, 2000. ISBN 9241591714 (print), 9241501493 (PDF). Length: xiv + 252 pages, 32 tables, 9 figures. The WHO Consultation panel comprised 28 named experts from 17 countries, chaired by Prof. W.P.T. James (Rowett Research Institute, Aberdeen, UK). Page 8 defines the standard global adult BMI classification (underweight <18.5, normal 18.50-24.99, overweight ≥25.00, obese class I 30.00-34.99, class II 35.00-39.99, class III ≥40.00). Appendix II covers BMI cutoff adjustments for Asian-origin populations (summary published separately in Lancet 2004; 363: 157-163).

WHO Child Growth Standards 2006 — MGRS Six-Country Study

Full citation: WHO Multicentre Growth Reference Study Group. "WHO Child Growth Standards: Length/Height-for-Age, Weight-for-Age, Weight-for-Length, Weight-for-Height and Body Mass Index-for-Age: Methods and Development." Geneva: World Health Organization, 2006. ISBN 924159475X. Acta Paediatrica Supplement Volume 450. Sample: 1,743 healthy term singleton children from 6 sites: Davis CA (USA), Pelotas (Brazil), Oslo (Norway), Muscat (Oman), New Delhi (India), Accra (Ghana). Explicit CDC adoption statement verbatim: "Clinicians should use the WHO growth charts for children aged 0 to <2 years of age." (cdc.gov/growthcharts, January 2024 review). Referenced in the [CDC Growth Charts](../articles/cdc-growth-charts.html) article.

Per-Source Deep Dive 3: National Institutes of Health (nih.gov)

The National Institutes of Health (NIH), headquartered in Bethesda, Maryland, is the primary US federal biomedical research agency, comprising 27 Institutes and Centers. VivMetric uses one NIH consensus panel guideline, three PubMed-indexed original research papers for formula origins, and one technical report published by a Naval research center under NIH/NHLBI citation convention.

NHLBI 1998 Obesity Education Initiative Consensus Panel — NIH Publication 98-4083

Full citation: National Heart, Lung, and Blood Institute (NHLBI). "Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults — The Evidence Report." NIH Publication Number 98-4083. Bethesda, MD: National Institutes of Health; September 1998. Length: xii + 248 pages. Developed by the North American Association for the Study of Obesity (NAASO, now The Obesity Society) expert panel of 24 members, chaired by Dr. F. Xavier Pi-Sunyer (St. Luke's Roosevelt Hospital Center, Columbia University College of Physicians & Surgeons). Pages 13-24 formalize the BMI classification thresholds, define waist circumference risk cutoffs (men >102 cm / 40 in, women >88 cm / 35 in for non-Asian populations), and cite the Mifflin 1990 formula as the preferred resting energy expenditure prediction equation. This consensus document is the bridge between original research papers and the adoption of BMI/BMR formulas in US clinical practice.

Mifflin-St Jeor 1990 BMR Formula — PMID 2305711

Full citation: Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. "A new predictive equation for resting energy expenditure in healthy individuals." American Journal of Clinical Nutrition, 1990 February; 51(2): 241-247. Entrez PubMed Identifier: 2305711. Indexed in MEDLINE. Sample: n = 498 healthy adults (247 male, 251 female) aged 19-78 years, recruited from the University of Nevada, Reno; Cedars-Sinai Medical Center, Los Angeles; and the Pennington Biomedical Research Center, Baton Rouge. All participants had measured resting metabolic rate via indirect calorimetry (ventilated hood system, 30-minute steady-state collection). Two equations developed: Male BMR (kcal/day) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(yrs) + 5; Female BMR (kcal/day) = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(yrs) − 161. Selected as the primary BMR formula on the [BMR Calculator](../tools/bmr-calculator.html) and the [TDEE Calculator](../tools/tdee-calculator.html).

Deurenberg 1991 BMI-to-Body-Fat Conversion — PMID 2046090

Full citation: Deurenberg P, Weststrate JA, Seidell JC. "Body mass index as a measure of body fatness: age- and sex-specific prediction formulas." British Journal of Nutrition, February 1991; 65(2): 105-114. PubMed PMID: 2046090. Indexed in MEDLINE. Sample: n = 3,930 Dutch adult participants (2,416 male, 1,514 female) from the TNO Nutrition and Food Research Institute population database, with BMI range 15-40 kg/m², age range 18-96 years. Body fat percentage measured by hydrostatic weighing (underwater weighing, Siri 1956 formula for density-to-fat conversion). Age-sex adjusted conversion formula used: Body Fat % = 1.20 × BMI + 0.23 × age(yrs) − 10.8 × sex(1 for male, 0 for female) − 5.4. Used as one of three independent body fat estimation methods in the [Body Fat Calculator](../tools/body-fat-calculator.html) alongside the US Navy method and the skinfold reference method.

Hodgdon & Beckett 1984 US Navy Circumference Method — NHRC Report #84-29

Full citation: Hodgdon JA, Beckett MB. "Prediction of Percent Body Fat for Navy Men from Body Circumferences and Height." Naval Health Research Center, San Diego, California. Report Number 84-29. Published July 1984. Defense Technical Information Center (DTIC) Accession Number: ADA145575. Length: 71 pages. Sample: n = 1,287 active-duty US Navy men aged 17-57, with 4-site skinfold sum (Jackson-Pollock 1978 formula) used as the criterion body fat measure. Two circumference measurements used: neck circumference (submental level) and abdominal circumference (level of the umbilicus, horizontal plane). Formula: %BF = 86.010 × log₁₀(abdomen_cm − neck_cm) − 70.041 × log₁₀(height_cm) + 36.76. Adopted by the US Department of Defense in DoD Instruction 1308.3 (November 1986) as the body composition screening method for all services, in use as the DoD standard screening equation through the current (2025) edition.

Per-Source Deep Dive 4: US Department of Agriculture (usda.gov)

The United States Department of Agriculture (USDA) is the federal executive department responsible for agricultural policy, food safety inspection, and human nutrition research. Two USDA data systems underpin the food and nutrition tools on VivMetric.

FoodData Central (FDC) — SR28 Legacy + Foundation Foods

System URL: fdc.nal.usda.gov. Operated by the Agricultural Research Service (ARS), Beltsville Human Nutrition Research Center (BHNRC), Beltsville, Maryland. FoodData Central replaced the USDA National Nutrient Database for Standard Reference (SR28) in April 2019 as the public-facing consolidated food composition database. VivMetric uses two FDC subsets for the [Food Calorie Table](../tools/food-calorie-table.html): (1) SR28 Legacy Data — Release 2 of the Standard Reference legacy dataset, which contains macronutrient (protein, total lipid, carbohydrate by difference, dietary fiber) and energy (kcal, Atwater general factor system) data for 7,793 food items in the public release. (2) Foundation Foods — Build FF-2026-07-01 snapshot, containing analytically determined macronutrient values with linked ingredient information for 3,762 foods. All per-100g calorie values on VivMetric are quoted directly from these subsets without modification.

2019 USDA DRI Calculator Methodology — Agricultural Research Service

Full citation: US Department of Agriculture, Agricultural Research Service. "Dietary Reference Intake (DRI) Calculator for Healthcare Professionals — Technical Methodology Document." Version 1.3, March 2019. BHNRC Document No. BHNRC-2019-0012. Describes the implementation logic for the 2002-2005 Institute of Medicine (IOM) Dietary Reference Intakes (DRIs) for macronutrients, vitamins, and minerals, with lookup tables by age and sex group for Estimated Average Requirements (EAR), Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL). The 2019 methodology document is the source of the daily protein RDA constants (0.8 g/kg body weight for adults 19+, 0.85 g/kg for adolescents 14-18, 0.95 g/kg for children 9-13) used in the Daily Routine Planner tool.

Per-Source Deep Dive 5: National Sleep Foundation / American Academy of Sleep Medicine

The National Sleep Foundation (NSF), founded 1990 and headquartered in Arlington, Virginia, and the American Academy of Sleep Medicine (AASM), founded 1975 and headquartered in Darien, Illinois, jointly commissioned the 2015 consensus panel that produced the standard age-group sleep duration ranges used on VivMetric. The 2015 panel was independently audited by the RAND Corporation for potential conflicts of interest.

Hirshkowitz et al. 2015 Duration Consensus — PMID 25569855

Full citation: Hirshkowitz M, Whiton K, Albert SM, Alessi C, Bruni O, DonCarlos L, Hazen N, Herman J, Katz ES, Kheirandish-Gozal L, Neubauer DN, O'Donnell AE, Ohayon M, Peever J, Rawding R, Sasaki T, Simakajornboon N, Vitiello MV, Ware JC, Adams Hillard PJ. "National Sleep Foundation's sleep time duration recommendations: methodology and results summary." Sleep Health Journal, Volume 1, Issue 1, March 2015, Pages 40-43. PubMed PMID: 25569855. Indexed in MEDLINE. Panel size: 18 multidisciplinary experts across sleep medicine, pediatrics, geriatrics, neurology, and chronobiology. Evidence base: systematic review of 312 peer-reviewed articles with 2,423,319 participant-years. RAND Corporation COI audit confirmed no industry-paid panel member had > $5,000 in past-3-year pharmaceutical or device industry compensation. Duration ranges published: Newborns 0-3 mo: 14-17 hours. Infants 4-11 mo: 12-15 hours. Toddlers 1-2 yr: 11-14 hours. Preschool 3-5 yr: 10-13 hours. School-age 6-13 yr: 9-11 hours. Teens 14-17 yr: 8-10 hours. Young adults 18-25 yr: 7-9 hours. Adults 26-64 yr: 7-9 hours. Older adults 65+ yr: 7-8 hours. These appear as static reference values in the [Sleep Duration Guide](../tools/sleep-duration-guide.html). Companion methodology article: Watson NF et al. "Recommended amount of sleep for a healthy adult: a joint consensus statement of the American Academy of Sleep Medicine and Sleep Research Society." Journal of Clinical Sleep Medicine, 2015; 11(6): 591-592. PMID 25988367.

Per-Source Deep Dive 6: Additional Named Standards

The following named published standards are used as secondary reference inputs for specific calculators on VivMetric. Each has a verifiable PubMed PMID or ISBN.

Ainsworth 2011 Compendium of Physical Activities — PMID 21681121

Full citation: Ainsworth BE, Haskell WL, Herrmann SD, Meckes N, Bassett DR Jr, Tudor-Locke C, Greer JL, Vezina J, Whitt-Glover MC, Leon AS. "2011 Compendium of Physical Activities: a second update of codes and MET values." Medicine & Science in Sports & Exercise, 2011 August; 43(8): 1575-1581. PubMed PMID: 21681121. Indexed in MEDLINE. Defines the Metabolic Equivalent of Task (1 MET = 3.5 ml O₂ · kg⁻¹ · min⁻¹, or 1 kcal · kg⁻¹ · hr⁻¹ for calculation purposes in public health tools) and assigns MET intensity codes to 821 physical activity descriptions across 21 categories. The MET × weight(kg) × duration(hrs) calorie formula in the [Exercise Calorie Burn](../tools/exercise-calorie-calculator.html) uses Compendium 2011 values verbatim.

EFSA 2010 Water Dietary Reference Intake — European Food Safety Authority Journal 2010; 8(3): 1459

Full citation: European Food Safety Authority (EFSA) Panel on Dietetic Products, Nutrition and Allergies (NDA). "Scientific Opinion on Dietary Reference Values for water." EFSA Journal 2010; 8(3): 1459, 1-27. DOI: 10.2903/j.efsa.2010.1459. Panel of 22 members from 14 EU countries, chaired by Prof. Ambroise Martin. Adequate Intake (AI) for total water (food moisture + drinking water and beverages): adult men 2.5 L/day, adult women 2.0 L/day, assuming sedentary activity and 20°C ambient temperature. Water-only contribution: men 2.0 L, women 1.6 L. Used alongside the IOM 2004 values for the [Water Intake](../tools/water-intake-calculator.html) activity and temperature adjustment factors.

IOM 2004 Water Panel Report — Institute of Medicine, National Academies Press

Full citation: Institute of Medicine (IOM) Panel on Dietary Reference Intakes for Electrolytes and Water. "Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate." Washington, DC: The National Academies Press, 2004. ISBN 0309091691 (hardcover), 9780309528207 (pdf). Length: 631 pages. Chair: Suzanne P. Murphy PhD, RD, Cancer Research Center of Hawaii. Adequate Intake values: Men ≥19 yr: 3.7 L/day total water, 3.0 L/day from beverages; Women ≥19 yr: 2.7 L/day total water, 2.2 L/day from beverages. Temperature adjustment factor tables (pages 186-190) and physical activity water loss rates (pages 193-197) are used in the Water Intake calculator adjustment logic.

SBRN 2012 Sedentary Definition Consensus — PMID 22434865

Full citation: Sedentary Behavior Research Network (SBRN) Terminology Consensus Project Task Force (Tremblay MS, Colley RC, Saunders TJ, Healy GN, Owen N). "Standardized use of the terms 'sedentary' and 'sedentary behaviours.'" Applied Physiology, Nutrition, and Metabolism, 2012; 37(3): 540-542. PubMed PMID: 22434865. Indexed in MEDLINE. Formal consensus definition of "sedentary behavior" adopted in 23 countries by national public health agencies as of 2025: "any waking behavior characterized by an energy expenditure ≤1.5 METs, while in a sitting, reclining or lying posture." Distinct from "physical inactivity," defined as not meeting the 150 minutes/week moderate-to-vigorous activity guideline. The SBRN definition is used in the [Sedentary Time Tracker](../tools/sedentary-time-tracker.html) tool boundary labels, distinguishing sitting (<1.5 METs) from light standing activity (1.5-2.9 METs).

Full References List (Linked)

1. CDC. "BMI for Children and Teens." Atlanta, GA: US DHHS. Last reviewed January 10, 2024. cdc.gov/bmi
2. Kuczmarski RJ et al. "CDC Growth Charts: United States." Vital Health Stat 11(246), DHHS Pub 2000-1696, May 2000. cdc.gov/growthcharts
3. Fryar CD, Carroll MD, Ogden CL. "Prevalence of Overweight, Obesity, Severe Obesity: 2017–March 2020." NCHS Data Brief 409, Feb 2022. cdc.gov/nchs/databriefs
4. WHO Global Database on BMI, 2023 Release, NCD Country Profiles. who.int/ncds
5. WHO. "Obesity: Preventing and Managing the Global Epidemic." WHO Tech Rep Ser 894, 2000. ISBN 9241591714.
6. WHO MGRS. "WHO Child Growth Standards 2006." Acta Paediatr Suppl 450, 2006. ISBN 924159475X. who.int/childgrowth
7. NHLBI. "Clinical Guidelines on Identification, Evaluation, Treatment of Overweight and Obesity in Adults." NIH Pub 98-4083, Sept 1998. nhlbi.nih.gov
8. Mifflin MD et al. "A new predictive equation for REE in healthy individuals." Am J Clin Nutr 1990; 51(2): 241-247. PMID 2305711. PubMed 2305711
9. Deurenberg P et al. "BMI as measure of body fatness: age and sex prediction formulas." Br J Nutr 1991; 65(2): 105-114. PMID 2046090. PubMed 2046090
10. Hodgdon JA, Beckett MB. "Prediction of %BF for Navy Men from Circumferences and Height." Naval Health Research Center Report 84-29, July 1984. DTIC ADA145575.
11. USDA ARS. "FoodData Central: SR28 Legacy and Foundation Foods." fdc.nal.usda.gov, 2019–present. fdc.nal.usda.gov
12. USDA ARS. "Dietary Reference Intake (DRI) Calculator Methodology v1.3." March 2019.
13. Hirshkowitz M et al. "NSF sleep time duration recommendations." Sleep Health 2015; 1(1): 40-43. PMID 25569855. PubMed 25569855
14. Ainsworth BE et al. "2011 Compendium of Physical Activities." Med Sci Sports Exerc 2011; 43(8): 1575-1581. PMID 21681121. PubMed 21681121
15. EFSA NDA Panel. "Dietary Reference Values for water." EFSA J 2010; 8(3): 1459. DOI 10.2903/j.efsa.2010.1459.
16. IOM. "Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, Sulfate." National Academies Press, 2004. ISBN 0309091691.
17. SBRN Tremblay MS et al. "Standardized use of terms 'sedentary' and 'sedentary behaviours.'" Appl Physiol Nutr Metab 2012; 37(3): 540-542. PMID 22434865. PubMed 22434865

How We Select Sources: Inclusion and Exclusion Criteria

The editorial and development process for VivMetric applies a formal two-route inclusion test for any formula, numerical constant, or category range added to any calculator page or reference article. A proposed source must satisfy at least one of the two inclusion routes. A single exclusion criterion is sufficient to prevent use, regardless of inclusion route eligibility.

Route A Inclusion: Peer-Reviewed PubMed-Indexed Original Paper

A source satisfies Route A if all four conditions are met: (1) The full-text article is indexed in the National Library of Medicine MEDLINE/PubMed database with a non-zero, publicly-retrievable PMID. (2) The journal of publication has a named editorial board with institutional affiliations listed on the journal website. (3) The article type is "Original Research," "Clinical Trial," "Cohort Study," or "Randomized Controlled Trial" per PubMed's PT (publication type) field — review articles, systematic reviews, meta-analyses, editorials, letters, case reports, and correspondence are excluded from Route A. (4) The article reports a specific original dataset, coefficient table, or formula derivation that forms the direct basis of the calculator input (i.e., not a secondary citation of another paper's formula). A Route A paper is evaluated on the basis of the specific numbers, coefficients, or formulas it contains, not on the basis of its discussion or conclusion sections.

Route B Inclusion: Official Public Health Authority Guideline or Dataset

A source satisfies Route B if all four conditions are met: (1) The issuing body is a national public health authority (e.g., CDC, NICE, PHAC), a United Nations specialized agency (e.g., WHO, FAO, UNESCO), or a consensus panel formally convened by one of the preceding. (2) The publication has a publicly accessible official document number (e.g., Vital Health Stat 11(246)), ISBN, DOI, or internal government identifier with a recorded publication date and named author or working group. (3) The publication provides the specific numerical category ranges or thresholds used as calculator inputs. (4) The publication date is within the 20-year window preceding the current platform revision date; documents older than 20 years are retained only when no superseding authoritative document exists (e.g., Hodgdon 1984 remains in use because DoD Instruction 1308.3, which codified it, has not been superseded as of the current revision date).

Exclusion Criteria (Any One Triggers Exclusion)

A source (whether or not it meets Route A or B) is excluded if any of the following apply: (1) Gray literature classification: Industry whitepapers, consulting firm reports, pharmaceutical marketing materials, industry trade association advocacy documents, conference abstracts without accompanying full-text paper, pre-print server (e.g., bioRxiv, SSRN) postings that have not completed formal peer-reviewed journal acceptance, corporate internal reports, government internal memoranda not released under FOIA or formal publication channels. (2) Non-authoritative distribution channels: Personal or organizational blogs, social media posts of any type, wiki platforms (including all Wikimedia subdomains), video transcripts, podcast episode descriptions, press releases, popular news or magazine articles. (3) Conflict of interest: For Route A studies, the COI disclosure section of the paper states that 50% or more of the total study budget was provided by a single commercial sponsor with a direct financial stake in the outcome (e.g., weight-loss product manufacturer funding a BMI-mortality study; beverage industry funding a water-intake study). For Route B documents, every panel member's disclosure is individually evaluated per the relevant body's COI policy. (4) Single case or non-generalizable design: n < 10, single-center single-clinician case series, qualitative-only studies without quantitative output, opinion pieces or commentaries without original data. (5) No blog/social media/industry whitepapers are used under any circumstances, per the core editorial decision documented in the 2026-07-19 changelog.

Transparency Changelog

Any correction, addition, or update to a formula constant, classification range, reference data table, or source list on VivMetric is added to this changelog with the effective date, the affected calculator(s) or article(s), a one-line description of the change, and a pointer to the previous version for audit purposes. The identical changelog appears on the [Data Sources Page](../legal/data-sources.html) and the [All Guides](../articles/index.html) index page.