# Sources & methodology

> How Courteous researches and cites etiquette guidance, which sources we trust, how we handle conflicting advice, and every source cited on the site.

URL: https://courteo.us/sources/

## Our approach

Etiquette sits between fact and custom. Some of what we publish is factual — the federal cash wage for tipped workers, the allergens that U.S. food labels must declare, how many Americans say they know their neighbors. Some is convention — where the dessert fork goes, how soon to send a thank-you note. We treat the two differently.

### Facts and statistics

- Every statistic links to the organization that published it, usually the original survey or study page.
- We prefer primary sources: government agencies (FDA, CDC, NIH, FAA, IRS, U.S. Department of State, UK Foreign, Commonwealth & Development Office), nonpartisan research organizations (Pew Research Center, Gallup), peer-reviewed research, and survey publishers that disclose their sample and dates (such as Bankrate's YouGov-fielded surveys).
- We state the year and, where useful, the sample of each survey, because tipping and technology habits change quickly.
- When a figure appears only in press coverage and we cannot confirm it at the source, we do not use it.

### Customs and recommendations

- For conventions, we compare established etiquette authorities and, for international customs, official tourism boards and government travel advice.
- Where authorities disagree, we say so and give a sensible default rather than pretending there is one right answer.
- Recommended tip ranges and similar guidelines are customary norms, not rules. Local practice varies.

### Updates

Each guide shows a "last updated" date. All guides were reviewed in October 2026. Links are checked automatically each time the site is built, and we replace sources that move or disappear.

### What we don't do

We do not accept payment for placement, publish sponsored etiquette advice, or fabricate quotes, studies, or "expert" sources. Links to sister sites in the allthingsN network are editorial and appear only where genuinely relevant.

## All cited sources (65)

### arxiv.org

- [Kooti et al., "Evolution of Conversations in the Age of Email Overload" (WWW 2015, arXiv)](https://arxiv.org/abs/1504.00704) Cited in: [Email etiquette](https://courteo.us/email-etiquette/)

### bankrate.com

- [Bankrate — Holiday tipping survey 2025 (YouGov, 2,445 U.S. adults, Oct. 2025)](https://www.bankrate.com/credit-cards/news/holiday-tipping-survey/) Cited in: [Holiday tipping guide](https://courteo.us/holiday-tipping/)
- [Bankrate — Press release: 63% of Americans have a negative view about tipping (June 2025)](https://www.bankrate.com/press-releases/63-of-americans-have-a-negative-view-about-tipping-with-41-saying-tipping-culture-has-gotten-out-of-control/) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/)
- [Bankrate — Tipping survey 2025 (YouGov, 2,277 U.S. adults, April 2025)](https://www.bankrate.com/personal-finance/tipping-survey/) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/)

### bps.org.uk

- [British Psychological Society Research Digest — Underestimating the power of gratitude](https://www.bps.org.uk/research-digest/underestimating-power-gratitude) Cited in: [Thank-you notes & templates](https://courteo.us/thank-you-notes/)

### celiac.org

- [Celiac Disease Foundation — What Is Celiac Disease?](https://celiac.org/about-celiac-disease/what-is-celiac-disease/) Cited in: [Allergies & dietary restrictions](https://courteo.us/dietary-restrictions-allergies/)

### chicagobooth.edu

- [Chicago Booth — Expressing your gratitude is more powerful than you think (Kumar & Epley, 2018)](https://www.chicagobooth.edu/media-relations-and-communications/press-releases/expressing-your-gratitude-is-more-powerful-than-you-think) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Email etiquette](https://courteo.us/email-etiquette/), [Thank-you notes & templates](https://courteo.us/thank-you-notes/), [Kids & manners](https://courteo.us/kids-manners/)

### convergencepolicy.org

- [Weber Shandwick, Powell Tate & KRC Research — Civility in America 2019 (PDF)](https://convergencepolicy.org/wp-content/uploads/2023/01/CivilityInAmerica2019SolutionsforTomorrow.pdf) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Social media etiquette](https://courteo.us/social-media-etiquette/)

### deutschland.de

- [deutschland.de — A guide to German etiquette](https://www.deutschland.de/en/topic/life/a-guide-to-german-etiquette) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)

### ecfr.gov

- [eCFR — 29 CFR Part 531 (tip credit and $2.13 cash wage)](https://www.ecfr.gov/current/title-29/subtitle-B/chapter-V/subchapter-B/part-531) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/)

### emilypost.com

- [Emily Post Institute — Basic Table Setting](https://emilypost.com/advice/basic-table-setting) Cited in: [Table manners](https://courteo.us/table-manners/)
- [Emily Post Institute — General Tipping Guide](https://emilypost.com/advice/general-tipping-guide) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/)
- [Emily Post Institute — Holiday Tipping Guide (USPS gift limits)](https://emilypost.com/advice/holiday-tipping-guide) Cited in: [Gift etiquette](https://courteo.us/gift-etiquette/), [Holiday tipping guide](https://courteo.us/holiday-tipping/)
- [Emily Post Institute — How Do I RSVP?](https://emilypost.com/advice/how-do-i-rsvp) Cited in: [RSVP etiquette](https://courteo.us/rsvp-etiquette/), [Wedding guest etiquette](https://courteo.us/wedding-guest-etiquette/)
- [Emily Post Institute — Invitation Etiquette](https://emilypost.com/advice/invitation-etiquette) Cited in: [Dinner party etiquette](https://courteo.us/dinner-party-etiquette/), [RSVP etiquette](https://courteo.us/rsvp-etiquette/), [Wedding guest etiquette](https://courteo.us/wedding-guest-etiquette/)
- [Emily Post Institute — Table Setting Guides](https://emilypost.com/advice/table-setting-guides) Cited in: [Table manners](https://courteo.us/table-manners/)
- [Emily Post Institute — Wedding Thank-Yous](https://emilypost.com/advice/wedding-thank-yous) Cited in: [Thank-you notes & templates](https://courteo.us/thank-you-notes/), [Wedding guest etiquette](https://courteo.us/wedding-guest-etiquette/)

### english.visitbeijing.com.cn

- [Visit Beijing — Etiquette for visitors](https://english.visitbeijing.com.cn/article/47OMmtlyGNh) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [Visit Beijing — Taboos and customs](https://english.visitbeijing.com.cn/article/47OMhDb1REF) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)

### faa.gov

- [FAA — Unruly Passengers](https://www.faa.gov/unruly) Cited in: [Airplane etiquette](https://courteo.us/airplane-etiquette/)

### fda.gov

- [U.S. Food and Drug Administration — FASTER Act: Sesame Is the Ninth Major Food Allergen](https://www.fda.gov/food/food-allergies/faster-act-sesame-ninth-major-food-allergen) Cited in: [Allergies & dietary restrictions](https://courteo.us/dietary-restrictions-allergies/)

### foodallergy.org

- [FARE — Facts and Statistics](https://www.foodallergy.org/resources/facts-and-statistics) Cited in: [Dinner party etiquette](https://courteo.us/dinner-party-etiquette/), [Allergies & dietary restrictions](https://courteo.us/dietary-restrictions-allergies/)

### foxnews.com

- [Fox News — Expedia Airplane Etiquette Study, conducted by GfK, 1,005 U.S. travelers (Jan. 2017)](https://www.foxnews.com/travel/these-are-most-annoying-airplane-passengers-according-to-expedia.amp) Cited in: [Airplane etiquette](https://courteo.us/airplane-etiquette/)

### france.fr

- [France.fr (Atout France) — Money in France](https://www.france.fr/en/article/money-france/) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/), [Tipping abroad](https://courteo.us/tipping-abroad/)

### gov.uk

- [GOV.UK — China travel advice: safety and security](https://www.gov.uk/foreign-travel-advice/china/safety-and-security) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [GOV.UK — France travel advice: safety and security](https://www.gov.uk/foreign-travel-advice/france/safety-and-security) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [GOV.UK — India travel advice: safety and security](https://www.gov.uk/foreign-travel-advice/india/safety-and-security) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [GOV.UK — Japan travel advice: safety and security](https://www.gov.uk/foreign-travel-advice/japan/safety-and-security) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [GOV.UK — Mexico travel advice: safety and security](https://www.gov.uk/foreign-travel-advice/mexico/safety-and-security) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [GOV.UK — United Arab Emirates travel advice: safety and security](https://www.gov.uk/foreign-travel-advice/united-arab-emirates/safety-and-security) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)

### hbr.org

- [Harvard Business Review — Porath & Pearson, The Price of Incivility (2013)](https://hbr.org/2013/01/the-price-of-incivility) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Customer-service phrases](https://courteo.us/customer-service-phrases/), [Workplace etiquette](https://courteo.us/workplace-etiquette/)

### incredibleindia.gov.in

- [Incredible India — Top Amritsar experiences](https://www.incredibleindia.gov.in/en/punjab/amritsar/25-top-amritsar-experiences-you-must) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)

### irs.gov

- [IRS — One Big Beautiful Bill Act: tax deductions for working Americans and seniors](https://www.irs.gov/newsroom/one-big-beautiful-bill-act-tax-deductions-for-working-americans-and-seniors) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/)

### japan.travel

- [Japan National Tourism Organization — Customs & manners](https://www.japan.travel/en/plan/custom-manners/) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [Japan National Tourism Organization — Japanese customs and etiquette](https://www.japan.travel/en/responsible-travel-guide/japanese-customs-and-etiquette/) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [Japan National Tourism Organization — Table manners in Japan](https://www.japan.travel/en/us/blog/table-manners-in-japan/) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/)
- [Japan National Tourism Organization — Tipping in Japan](https://www.japan.travel/en/plan/tipping-in-japan/) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/), [Tipping abroad](https://courteo.us/tipping-abroad/)

### kvia.com

- [CNN via KVIA — 2021 was the year of the unruly airline passenger (Jan. 2022)](https://kvia.com/entertainment/cnn-style/2022/01/13/2021-year-of-the-unruly-airline-passenger/) Cited in: [Airplane etiquette](https://courteo.us/airplane-etiquette/)

### law.cornell.edu

- [Cornell LII — 29 U.S. Code § 203 (definition of tipped employee)](https://www.law.cornell.edu/uscode/text/29/203) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/)

### microsoft.com

- [Microsoft WorkLab — Breaking down the infinite workday (Work Trend Index, June 2025)](https://www.microsoft.com/en-us/worklab/work-trend-index/breaking-down-infinite-workday) Cited in: [Email etiquette](https://courteo.us/email-etiquette/), [Video call etiquette](https://courteo.us/video-call-etiquette/), [Workplace etiquette](https://courteo.us/workplace-etiquette/)
- [Microsoft WorkLab — The next great disruption is hybrid work (Work Trend Index 2021)](https://www.microsoft.com/en-us/worklab/work-trend-index/hybrid-work) Cited in: [Video call etiquette](https://courteo.us/video-call-etiquette/), [Workplace etiquette](https://courteo.us/workplace-etiquette/)

### news.gallup.com

- [Gallup — In U.S., 4% Identify as Vegetarian, 1% as Vegan (2023)](https://news.gallup.com/poll/510038/identify-vegetarian-vegan.aspx) Cited in: [Dinner party etiquette](https://courteo.us/dinner-party-etiquette/), [Allergies & dietary restrictions](https://courteo.us/dietary-restrictions-allergies/)

### news.harvard.edu

- [Harvard Gazette — The power of thanks (Grant & Gino research)](https://news.harvard.edu/gazette/story/2013/03/the-power-of-thanks/) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Customer-service phrases](https://courteo.us/customer-service-phrases/), [Thank-you notes & templates](https://courteo.us/thank-you-notes/), [Workplace etiquette](https://courteo.us/workplace-etiquette/)

### news.uchicago.edu

- [UChicago News — People underestimate the value of sending letters of appreciation](https://news.uchicago.edu/story/people-underestimate-value-sending-letters-appreciation) Cited in: [Thank-you notes & templates](https://courteo.us/thank-you-notes/), [Kids & manners](https://courteo.us/kids-manners/)

### news.usps.com

- [USPS News — Facts on paper: greeting card statistics (citing the Greeting Card Association)](https://news.usps.com/2019/09/26/facts-on-paper/) Cited in: [Condolence etiquette](https://courteo.us/condolence-etiquette/), [Gift etiquette](https://courteo.us/gift-etiquette/)

### niddk.nih.gov

- [NIDDK (National Institutes of Health) — Definition & Facts for Celiac Disease](https://www.niddk.nih.gov/health-information/digestive-diseases/celiac-disease/definition-facts) Cited in: [Allergies & dietary restrictions](https://courteo.us/dietary-restrictions-allergies/)

### pewresearch.org

- [Pew Research Center — Almost half of Americans say people have gotten ruder since the COVID-19 pandemic (Mar. 2025)](https://www.pewresearch.org/short-reads/2025/03/12/almost-half-of-americans-say-people-have-gotten-ruder-since-the-covid-19-pandemic/) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Customer-service phrases](https://courteo.us/customer-service-phrases/), [Texting & phone etiquette](https://courteo.us/texting-phone-etiquette/)
- [Pew Research Center — Americans and Text Messaging (2011)](https://www.pewresearch.org/internet/2011/09/19/americans-and-text-messaging/) Cited in: [Texting & phone etiquette](https://courteo.us/texting-phone-etiquette/)
- [Pew Research Center — Americans’ Views on Mobile Etiquette (Aug. 2015)](https://www.pewresearch.org/internet/2015/08/26/americans-views-on-mobile-etiquette/) Cited in: [Table manners](https://courteo.us/table-manners/), [Texting & phone etiquette](https://courteo.us/texting-phone-etiquette/)
- [Pew Research Center — Families may differ, but they share common values on parenting (Sept. 2014)](https://www.pewresearch.org/short-reads/2014/09/18/families-may-differ-but-they-share-common-values-on-parenting/) Cited in: [Kids & manners](https://courteo.us/kids-manners/)
- [Pew Research Center — How connected do Americans feel to their neighbors? (May 2025; survey of 9,482 adults, March 2025)](https://www.pewresearch.org/short-reads/2025/05/08/how-connected-do-americans-feel-to-their-neighbors/) Cited in: [Neighbor etiquette](https://courteo.us/neighbor-etiquette/)
- [Pew Research Center — Mobile Fact Sheet (2026)](https://www.pewresearch.org/internet/fact-sheet/mobile/) Cited in: [Texting & phone etiquette](https://courteo.us/texting-phone-etiquette/)
- [Pew Research Center — Parenting in America Today (Jan. 2023 report, PDF)](https://www.pewresearch.org/wp-content/uploads/sites/20/2023/01/PST_2023.01.24_parenting_REPORT.pdf) Cited in: [Kids & manners](https://courteo.us/kids-manners/)
- [Pew Research Center — Social Media Fact Sheet (2026)](https://www.pewresearch.org/internet/fact-sheet/social-media/) Cited in: [Social media etiquette](https://courteo.us/social-media-etiquette/)
- [Pew Research Center — The State of Online Harassment (Jan. 2021)](https://www.pewresearch.org/internet/2021/01/13/the-state-of-online-harassment/) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Social media etiquette](https://courteo.us/social-media-etiquette/)
- [Pew Research Center — Tipping Culture in America: Public Sees a Changed Landscape (Nov. 2023)](https://www.pewresearch.org/2023/11/09/tipping-culture-in-america-public-sees-a-changed-landscape/) Cited in: [How much to tip (US guide)](https://courteo.us/tipping-guide/), [Tipping abroad](https://courteo.us/tipping-abroad/)

### pmc.ncbi.nlm.nih.gov

- [Gupta et al., Prevalence and Severity of Food Allergies Among US Adults, JAMA Network Open (2019), via PubMed Central](https://pmc.ncbi.nlm.nih.gov/articles/PMC6324316/) Cited in: [Allergies & dietary restrictions](https://courteo.us/dietary-restrictions-allergies/)

### restaurantdive.com

- [Restaurant Dive — OpenTable launches initiative to combat diner no-shows (June 2021)](https://www.restaurantdive.com/news/opentable-launches-initiative-to-combat-diner-no-shows/602034/) Cited in: [RSVP etiquette](https://courteo.us/rsvp-etiquette/), [Table manners](https://courteo.us/table-manners/)

### shrm.org

- [SHRM — Incivility reaches record high (Civility Index, Q4 2024)](https://shrm.org/about/press-room/incivility-reaches-record-high-with-political-viewpoint-differen) Cited in: [Are people getting ruder?](https://courteo.us/state-of-civility/), [Customer-service phrases](https://courteo.us/customer-service-phrases/), [Workplace etiquette](https://courteo.us/workplace-etiquette/)

### vhil.stanford.edu

- [Stanford Virtual Human Interaction Lab — Bailenson, Nonverbal Overload: A Theoretical Argument for the Causes of Zoom Fatigue (2021)](https://vhil.stanford.edu/publications/social-interaction/nonverbal-overload-theoretical-argument-causes-zoom-fatigue) Cited in: [Video call etiquette](https://courteo.us/video-call-etiquette/)

### visitberlin.de

- [visitBerlin — Etiquette & tipping](https://www.visitberlin.de/en/etiquette-tipping) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/), [Tipping abroad](https://courteo.us/tipping-abroad/)

### visitbritain.com

- [VisitBritain — The British pub](https://www.visitbritain.com/en/things-to-do/british-pub) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/), [Tipping abroad](https://courteo.us/tipping-abroad/)
- [VisitBritain — Useful information](https://www.visitbritain.com/en/plan-your-trip/useful-information) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/), [Tipping abroad](https://courteo.us/tipping-abroad/)

### visitmexico.com

- [Visit México — Frequently asked questions](https://visitmexico.com/en/pagina/preguntas-frecuentes) Cited in: [Cultural etiquette by country](https://courteo.us/cultural-etiquette-by-country/), [Tipping abroad](https://courteo.us/tipping-abroad/)

### zola.com

- [Zola — The First Look Report 2026](https://www.zola.com/expert-advice/the-first-look-report) Cited in: [Gift etiquette](https://courteo.us/gift-etiquette/), [Wedding guest etiquette](https://courteo.us/wedding-guest-etiquette/)

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Courteous (courteo.us) — Modern manners, researched. Markdown version of https://courteo.us/sources/