6 Solo Investing, Digital-Asset & Royalty Businesses

The 6 companies

#41 · 自出版书系 KDP 版税（Hugh Howey《Wool/Silo》）

Investing, Digital Assets & Royalties · Hugh Howey and other independent authors, United States · Founded 2011 · Inspiration Index 69/100

Write once, earn for years: a solo author turns one book series into a stacking portfolio of royalty-bearing digital assets.

• Cumulative sales: Millions of copies, 40+ languages (the Silo series)
• Royalty income: Online royalties >$1M (per author, as of 2013)
• High-earning author base: 2,000+ KDP authors earned >$100K in royalties in 2022 (Amazon)
• Team: 1 (the author; covers and editing outsourced)
• Founded: 2011

Background. In July 2011 Howey self-published the novelette Wool to Amazon KDP at $0.99; with zero marketing it spread on word of mouth and grew into a series within six months. By 2013 his online royalties had crossed seven figures, and he turned down million-dollar traditional-publishing offers, signing only a ~$500K print-only deal while retaining all digital and audio rights. In 2023 the series was adapted into the Apple TV+ show Silo, amplifying long-tail royalties again.

Business model. The core revenue is KDP e-book royalties: titles priced $2.99–$9.99 earn a 70% share, with 35% outside that band; books can also enroll in Kindle Unlimited and draw from a monthly global fund per page read (KENP) at roughly $0.004–0.005/page. A single act of writing creates a permanently saleable digital asset, and multiple titles cross-promote into a series funnel. Layered on top are print, audio, foreign-language and screen-adaptation rights, producing multiple tiers of passive cash flow.

Growth levers.

• Series funnel: a low-priced or free first volume pulls readers in, later volumes sell at full price, and finishing one book leads naturally to the next.
• Retain digital and derivative rights: license out only print distribution and keep the high-margin e-book, audio and screen rights in-house.
• Reuse one IP across formats and languages: e-book to print to audio to 40+ languages to screen, selling the same content many times over.
• Data-driven pricing and listing: Howey co-founded Author Earnings to scrape real sales data and calibrate strategy.

Replicable takeaways.

• Treat a book as an asset, not a project: once written it sells passively for years; the goal is to compound a portfolio, not chase a single hit.
• Guard high-margin rights: don't sell off what you can distribute yourself (e-book, audio); let traditional publishers handle only the print channel they're good at.
• Build a repeat-purchase funnel with a series plus a lead-in first volume; single titles rarely work, but a set compounds.
• Start-up cost is minimal (only outsourced covers and editing), so validate first and scale later, with limited downside if it fails.

Risk & moat. The moat is an accumulated reader base, brand IP and a series repeat-purchase funnel, so old titles keep throwing off long-tail royalties. The biggest risk is platform dependence and channel concentration: a single Amazon change to royalty rates or the KU fund directly cuts income. A secondary threat is a flood of AI-generated books saturating the category and diluting search (NPR and Rolling Stone reported in 2024 that KDP is being swamped by AI knockoffs), and the ceiling is that success leans heavily on book quality and luck, making hits hard to replicate at scale.

Stack. Amazon KDP (e-book and print-on-demand) + KDP Select/Kindle Unlimited + ACX audio; covers, editing and layout outsourced; own website and email list to build a direct reader base.

Revenue 7/10 · Replicability 6/10 · Leverage 9/10 · Timeliness 6/10

Sources & confidence. Wikipedia: Hugh Howey / Silo (series) — sales, rights, Apple TV+ timeline · Amazon KDP official help pages — 70%/35% royalties and the Kindle Unlimited KENP page-read fund · aboutamazon.com — 2,000+ KDP authors earned >$100K in 2022; the >$50K cohort grew ~40% from 2020–2022 · Hugh Howey's Author Earnings reports — self-publishing's 70% vs. traditional 17.5% royalty share · NPR / Rolling Stone (2024) — KDP swamped by AI-generated and counterfeit books — Medium — royalty mechanics, industry structure and timeline are high-confidence from official/authoritative sources; Howey's exact '>$10M royalties, >3M copies' figures are not fully verified publicly, so they have been downgraded to the provable 'millions of copies, online royalties >$1M (self-reported, 2013).'

#63 · Long Tail Pro / 利基站组合 (Spencer Haws)

Investing, Digital Assets & Royalties · Spencer Haws, United States · Founded 2011 · Inspiration Index 64/100

Treat content sites as tradable assets: build them in bulk for ad-affiliate cash flow, then productize and sell at a multiple.

• Niche Pursuits revenue: ~$5M/year, ~$417K/month (Starter Story est.)
• Exits: Long Tail Pro, seven figures (2016); OwnTheYard site, >$250K (2019)
• Build scale: ~200 niche sites built in 2010 alone
• Team: Solo at start; now small team + freelancers + co-founded venture (Motion Invest)
• Went full-time: 2011, after quitting his job

Background. Spencer Haws worked in corporate banking at Wells Fargo and began studying SEO on the side in 2006. In 2010 he built ~200 niche sites targeting low-competition keywords and monetized them via AdSense; by early 2011 they earned ~$10K/month, prompting him to quit in March and go full-time while documenting everything on his blog Niche Pursuits. He turned his own site-building pain points into the keyword tool Long Tail Pro, which scaled fast precisely because he was its target user.

Business model. A two-engine model: operating cash flow plus asset exits. Niche content sites earn AdSense, Amazon Associates and display-ad revenue, while the Niche Pursuits blog and podcast earn affiliate commissions, sponsorships and course/membership sales. The productization arm turns hard-won experience into software sold at high multiples: Long Tail Pro (a $97-tier keyword tool) sold a majority stake for seven figures in 2016, Link Whisper (a WordPress internal-linking plugin, ~$97/year) and an Amazon FBA business were later sold, and the public case-study site OwnTheYard was grown to ~$1.2K/month and sold for >$250K. Haws then co-founded the site marketplace Motion Invest, making the buying and selling of sites itself a business.

Growth levers.

• Bulk site-building: use keyword tools to systematically surface low-competition terms, building ~200 sites in a year to spread single-site risk
• Build-in-public marketing: turn the full build-and-sell process into the Niche Site Project series and monthly income reports, funneling attention back to the blog, tools and courses
• Productize and exit: convert personal pain points into SaaS/plugins (Long Tail Pro, Link Whisper), exit at high EBITDA multiples, then turn 'selling sites' into a marketplace (Motion Invest)

Replicable takeaways.

• Treat a website as an asset, not a project: design the cash-flow model and exit path (priced at ~30-40x monthly net profit) from day one
• Productize pain you personally feel: Long Tail Pro scaled fast because the founder was the target user
• Build in public to compound trust and traffic, then let the blog and audience cold-start every new product
• Diversify away single-site and single-algorithm risk: multiple sites plus multiple revenue streams (ads, affiliate, tools, marketplace) hedge Google updates

Risk & moat. The moat is a durable audience and brand trust (the Niche Pursuits blog and podcast) plus first-hand operating data, giving its tools and courses native distribution. The biggest risk is heavy dependence on Google's algorithm and affiliate policies—updates like HCU can wipe out a pure-SEO niche site's cash flow overnight. With AI content flooding search and Google cracking down, bulk site-building faces diminishing returns, pushing the ceiling toward more cycle-resistant tools and marketplaces.

Stack. WordPress + AdSense/Amazon Associates + display-ad networks; in-house SaaS (Long Tail Pro) and plugin (Link Whisper); podcast + email list + membership courses; outsourced writers/developers; co-runs the Motion Invest marketplace.

Revenue 7/10 · Replicability 5/10 · Leverage 8/10 · Timeliness 6/10

Sources & confidence. Niche Pursuits official post: 'How and Why I Sold My Software Company' (Long Tail Pro, 2016) · Niche Pursuits: 'The Conclusion of Niche Site Project 4' (OwnTheYard >$250K, 2019) · Niche Pursuits 'About Me' page (timeline; ~200 sites built in 2010; quit job in 2011) · Starter Story: Niche Pursuits breakdown (~$5M/year revenue est.) · Motion Invest official site and The Website Flip review (founded 2019; 1,500+ sites sold by 2024) — Medium — timeline, exits and build scale are first-hand founder disclosures and highly credible, but Long Tail Pro's exact sale price (seven figures; reportedly ~$1.8M at est. 80%) and current Niche Pursuits/Link Whisper revenue are third-party estimates the founder has not precisely confirmed.

#68 · 独立字体设计师 / 单人字库（版税型）｜样本：Set Sail Studios（Sam Parrett）

Investing, Digital Assets & Royalties · Independent type designer (category sample: UK's Sam Parrett / Set Sail Studios; premium comparison: New Zealand's Kris Sowersby / Klim), Multiple · Founded 2014 · Inspiration Index 63/100

Draw a typeface once, license it forever: a solo designer turns one font into a royalty asset the world pays for repeatedly.

• Sample net revenue: ~$7,000/month (Set Sail Studios, after MyFonts' 50% cut, per The Hustle)
• Catalog: 100+ font families released to date (drawn once, sold for years)
• Channel split: MyFonts/Creative Market take 50%; industry reseller royalties typically 30-50%
• Team: 1 person (self-drawn, self-run; leaders like Klim run 2-6-person teams)
• Founded: First font shipped 2014; full-time on fonts from 2015

Background. Sam Parrett spent ~6 years as a freelance graphic designer in the music industry; tired of reusing the same fonts, he reworked an old hand-lettered logo exercise into his first typeface, launched in 2014, and went full-time a year later. His brush-script style found traction on MyFonts and Creative Market, converting one-off design commissions into a font catalog that sells indefinitely. The category is structurally similar: ~4,500 foundries sell 250,000+ fonts on MyFonts, most of them solo or very small teams.

Business model. The core is a 'design once, license forever' royalty asset: retail sales run through MyFonts, Creative Market, Etsy and a self-owned site, priced by license type (desktop/web/app/print) at an average of ~$29, with platforms taking ~50%; direct sales keep the full amount but require self-built traffic. The long tail comes from OEM licensing—embedding fonts in devices, software and system UIs (phones, TVs, car displays, printing presses)—where deals are large, can land years after release, and form an underrated 'passive' cash flow. MyFonts alone delivers the sample ~$7K/month net.

Growth levers.

• High output plus hits drive the tail: keep shipping new fonts (100+ families) and let a few bestsellers like Northwell pull exposure and bundle sales across the whole catalog
• Multi-channel distribution: tap ready-made traffic on MyFonts/Creative Market/Etsy, then use the owned site for high-margin direct sales and brand-building, diluting platform dependence
• Tiered licensing: bill the same typeface by desktop/web/app/OEM at different price points and volumes, mining high-ticket OEM/enterprise licenses from brands and device makers

Replicable takeaways.

• Build assets, not commissions: turn reusable design into standardized products you can license repeatedly, decoupling revenue from hours
• Validate selection on platform traffic first, then use an owned site to keep the high margins of your bestsellers
• Split license terms finely (use x volume x OEM) so one creation spans the full price band from $29 personal use to five-figure enterprise/device deals
• Enforcement is revenue: roughly half the sample's customers arrive via 'pirate first, license later'—actively policing usage converts directly into retroactive licensing income

Risk & moat. The moat lies in style recognizability, the compounding long tail of a large catalog, and licensing relationships with platforms and brands. The biggest risk is channel concentration in the Monotype family (MyFonts takes 50% and controls pricing and exposure), so a single policy change hits revenue; downside also includes piracy and enforcement costs, plus AI-generated fonts and abundant free fonts (Google Fonts) depressing long-tail prices. The ceiling is one person's production and marketing bandwidth—without scale it stays a 'passive side income' tier.

Stack. Glyphs/FontLab for type design plus Illustrator for hand-drawn vectorization; distribution via MyFonts/Creative Market/Etsy plus an owned site; royalties/reconciliation settled by Monotype's platform; solo-run, self-marketed.

Revenue 5/10 · Replicability 6/10 · Leverage 9/10 · Timeliness 6/10

Sources & confidence. The Hustle, 'Where do fonts come from?'—Sam Parrett at ~$7,000/month (after the 50% cut), MyFonts' 4,500 foundries / 250,000+ fonts, ~$29 average price, 50% platform cut · Monotype 2022 survey: 433 independent foundries report Monotype royalties as >=50% of total revenue, nearly 1/4 at >=75%; ~55% treat it as passive income, 45% rely on font sales for a living · Set Sail Studios site/About and Vintage Type / Linseed / YouWorkForThem interviews: 2014 debut, full-time from 2015, 100+ font families, clients including Victoria's Secret/Starbucks/Adobe · Typographica, 'Taking Your Fonts to Market'; Type Fleet/Klim OEM licensing terms: 30-50% reseller royalties, perpetual OEM licenses and long-tail characteristics · Klim Type Foundry (Kris Sowersby, direct-sales model) as a premium comparison (small team, not strictly solo) — Medium — category-structure data (Monotype 433-foundry survey, 50% cut, ~$29 average) comes from reliable reporting and official sources and is high-confidence, but the solo income figure rests on a single case (Set Sail Studios) relayed by The Hustle (~$7K/month, MyFonts channel only), without itemized founder disclosure.

#72 · SHL Capital（个人 Rolling Fund / 单人天使，Sahil Lavingia）

Investing, Digital Assets & Royalties · Sahil Lavingia, United States · Founded 2020 · Inspiration Index 62/100

A solo GP running an eight-figure fund off a Notion memo and a few tweets, with AngelList handling the back office.

• Annual commitments: ~$5M/yr at launch, peaking ~$10M+/yr (some sources cite $15M+)
• First-quarter raise: >$1M (vs. $100K target; hit SEC subscriber cap)
• Check size: $100K–$250K per deal
• Team: 1 (back office fully outsourced to AngelList)
• Operating period: Aug 2020 – Jul 2024 (wound down)

Background. Lavingia founded Gumroad in 2011 and, after deep layoffs in 2019, rebuilt it into a profitable company with almost no full-time staff. In August 2020 he became one of AngelList's first rolling-fund managers: armed with a single Notion memo, a few tweets and a Zoom watched by 1,800 people (raising publicly under SEC Reg 506(c)), he turned a $100K first-quarter target into over $1M and hit the subscriber cap. He announced the wind-down in July 2024, with ~$155K still to deploy.

Business model. A rolling fund is a series of quarterly-raised sub-funds: the GP never has to close one large vehicle, and LPs subscribe each quarter (often from $5K–$10K/quarter), while AngelList runs all fund administration, compliance, wire transfers and reporting. GP economics are two-part: a ~2% annual management fee (a $5M fund yields ~$100K/yr gross) plus ~20% carry on exits, accrued across the full subscription period under the rolling structure. AngelList takes ~2% plus a $25K/quarter platform fee. In effect it compresses the traditional $200K+, multi-month fund build into a standardized product one person can run—where the real money sits in carry, not fees.

Growth levers.

• Ride platform infrastructure: legal, compliance, wiring, reporting and tax are all outsourced to AngelList, so one person can perform the full GP role.
• Distribute through a personal audience: as a known founder (Gumroad, large Twitter following), fundraising became public tweets plus a Zoom under Reg 506(c)—oversubscribed 10x in the first quarter.
• Anchor with marquee LP backing: capital from Naval Ravikant, Josh Kopelman (First Round) and Arlan Hamilton conferred instant credibility and deal flow.
• Low activation energy, stackable: the rolling structure starts small and scales committed capital quarter by quarter, with no need to first close a large fund.

Replicable takeaways.

• Build the audience before the fund: distribution (following, reputation, deal flow) is the solo GP's real moat; the platform only solves the back office.
• Treat fund-launching as a product, not a project: standardized administration lets one person raise and deploy capital compliantly, dropping the barrier from hundreds of thousands of dollars to thousands.
• Understand the income structure: fees barely sustain you ($5M x 2% ≈ $100K gross, thinner after platform fees); the real return is carry locked 5–10 years out, so you need outside cash flow to bridge it.
• Use public solicitation to amplify reach: within the Reg 506(c) framework, going public with the raise taps an LP pool far beyond private contacts.

Risk & moat. The moat is the founder's personal brand, marquee LP backing and proprietary deal flow—portable across vehicles but not replaceable by the platform, which only commoditizes the back office. The biggest risk is that returns hinge almost entirely on unrealized carry that needs 5–10 years to prove out and was never publicly disclosed here. The GP is also a single point of energy and reputation: Lavingia wound down in July 2024 to return to Gumroad, underscoring how hard it is to run a company and a fund at once.

Stack. AngelList Rolling Funds (fund admin/compliance/SPV/wiring/reporting) + Notion (raise memo) + Twitter/X + Zoom (distribution) + SEC Reg 506(c) compliance framework

Revenue 6/10 · Replicability 4/10 · Leverage 9/10 · Timeliness 7/10

Sources & confidence. Sahil Lavingia public tweets (@shl): rolling fund wind-down, $1,555,691.52 left to deploy (2024-07) · AngelList blog: Gumroad CEO's first $1M+/quarter rolling fund raise recap · TechCrunch (2020-08): Gumroad founder launches seed fund with AngelList · 20VC / Venture Unlocked podcast interviews: rolling fund mechanics and solo-GP economics · vcsheet.com SHL Capital profile; AngelList official Rolling Funds fee/mechanics documentation — Medium — structure, timeline, raise method and LPs are corroborated across multiple public sources, but AUM figures vary ($5M/$10M/$15M) and actual fund returns (IRR/MOIC) were never disclosed, so investment performance is unverifiable.

#76 · 利基内容站 Flip（Empire Flippers 市场样本）

Investing, Digital Assets & Royalties · Solo seller / independent site-builder (market sample; representative operator e.g. Shawna Newman), Multiple · Founded 2014 · Inspiration Index 62/100

Build an ad- and affiliate-funded niche content site, grow its cash flow, then exit at a profit multiple through a brokered marketplace.

• Platform cumulative GMV: ~$589M (EF Scoreboard 2025)
• Cumulative deals closed: 2,600+ (EF 2025)
• Buyer/seller community: ~325,000 people
• Benchmark flip: $3,164 buy-in to $40,000 sale (303 days, 1,164% ROI)
• Team: 1 person (content and links outsourced)

Background. The playbook begins with a solo operator using content plus affiliate and display ads to grow a niche site to steady monthly profit, then listing it for exit on a broker marketplace. Empire Flippers (launched 2011, marketplace operations from 2014) standardized this path: valuation on a monthly net-profit multiple, escrowed verification, and managed handover. Representative operator Shawna Newman, building since 2009, has sold 30+ self-built sites since 2014, proving a single person can close the loop.

Business model. Money comes from two layers: the asset's own cash flow (affiliate commissions, display ads, private ad sales, info products) and multiple arbitrage on exit. Content sites typically value at 20-60x monthly net profit (~27x in 2024), converting a site earning a few thousand dollars a month into a one-time payout of tens to hundreds of thousands. EF charges no listing fee and takes tiered commission (15% in the $66.7K-$700K band, dropping to 8% / 2.5% higher up); listing requires ~$2,000 monthly net profit and 12 months of data, with an average ~120-day sale cycle closing at ~87% of asking price.

Growth levers.

• Front-load a ~100-article content sprint in the first 3 months for fast traction, then diversify traffic from Google to Pinterest and email to cut single-channel risk and lift the valuation
• Hold 18-24 months to stabilize monthly profit, layering CRO and new monetization channels (e.g. Amazon Associates, private ad sales) to raise both the profit base and the multiple
• Use a third-party broker as the trust and liquidity layer: escrowed verification plus managed handover standardize deals that are hard to close privately, enabling repeatable exits at a premium multiple

Replicable takeaways.

• Run a website as a valuable asset: track monthly net profit and the multiple, and engineer for exit from day one (clean data, diversified traffic, verifiable profit)
• Pick trend-driven niches and start cheap: the benchmark $3,164 entry rode a rising topic to a 1,164% return in 303 days, where timing and topic selection beat sheer volume
• Outsource the bottlenecks and own the core: contract out content and link-building, keep decisions and monetization in-house, so one person can roll build-grow-sell across multiple sites

Risk & moat. The moat is the broker's trust, escrow, and liquidity network plus the seller's accumulated feel for topic selection, site-building, and monetization, not any individual monopoly. The biggest risk and ceiling: Google algorithm changes and AI Overviews squeeze affiliate-content traffic, dragging valuation multiples down (content-site multiples and deal volume fell markedly in 2025 versus 2023). Per-site upside caps at monthly profit, so scaling means repeating build-and-sell rather than compounding.

Stack. WordPress build + affiliate / AdSense / private ad-sale monetization + outsourced writers and link-building; exit via Empire Flippers (escrowed verification, managed handover, multiple-based valuation), with peers Flippa, Motion Invest, Investors Club.

Revenue 6/10 · Replicability 6/10 · Leverage 8/10 · Timeliness 5/10

Sources & confidence. Empire Flippers Scoreboard (live GMV / deal count / cycle, empireflippers.com/scoreboard) · Empire Flippers, "7 Tips for Solo Site Building & Flipping" (Shawna Newman's solo build-and-sell playbook) · Empire Flippers Content Sites ROI Study + flipped-businesses-data ($3,164 to $40,000, 1,164% ROI case) · Empire Flippers commission structure and listing-threshold docs / Investors Club fee breakdown — Medium - EF's aggregate data (GMV, deal count, multiples, commissions) and the benchmark flip figures are verifiable on official EF pages; but the 'solo seller' is a market sample, not a single disclosed subject, so the single case is illustrative rather than broadly representative.

#85 · Park.io（ccTLD 过期域名抢注与拍卖）

Investing, Digital Assets & Royalties · Mike Carson, United States · Founded 2014 · Inspiration Index 60/100

A solo founder scripted expiring-ccTLD backordering into seven-figure annual revenue, then sold the platform itself as a digital asset.

• Revenue: ~$125K/mo (2016, per IH); peak ~$150K/mo
• Gross margin: ~70% (est., per interviews)
• Team: 1 (founder; $0 raised)
• Founded: June 2014
• Exit: Acquired by Dynadot, Oct 2023 (amount undisclosed)

Background. Carson wanted smile.io and wrote a script polling domain availability every second, yet still missed it by minutes. He productized the script in about a week—UI, registration, and payments—and closed his first sale on launch day. Annual revenue passed $1M within two years, run entirely by him; he publicly listed the business at $1.5M in 2016 and ultimately sold to Dynadot in 2023.

Business model. Park.io focused on ccTLDs popular with hackers (.io/.ly/.me/.ai/.gg/.co) and let users backorder expiring domains, charging only on a successful catch. A single backorder cost a flat $99; when multiple users wanted the same name it triggered a 10-day auction to the highest bidder. Stripe handled payments, and roughly half of revenue came from platform catch fees and half from Carson reselling domains he held himself.

Growth levers.

• Self-compounding acquisition: every caught domain pointed to a uniform parking page that funneled traffic back to Park.io, driving near-zero-cost word-of-mouth growth.
• Scripting every manual step—monitoring, catching, transfers, weekly reports—so one person carried $125K/mo, described by the founder as 'like having a 24-hour team.'
• Donating relevant domains (angular.io, perl.io, gnome.io) to open-source foundations to earn exposure and developer-community trust.

Replicable takeaways.

• Solve your own real pain with a script first, then productize it—an MVP can ship in a week and close a sale on day one.
• Charge only on success ($99) and convert contested names into auctions: a pricing model that lowers the decision barrier while automatically capturing high-value assets.
• Build 'marketing' into the product (parking pages, domain donations) rather than buying traffic; a solo founder's leverage comes from automation, not headcount.
• A cash-flowing indie project is itself a valuable, sellable digital asset—design for exit early.

Risk & moat. The moat is catch speed (scripting engineering), first-mover coverage of niche ccTLDs, and the parking-page acquisition flywheel. The biggest risk is registries building their own backordering—the .io operator later did launch a competitor, which Carson absorbed through adaptation—plus a ceiling set by ccTLD expiry supply and one person's capacity; with the model heavily dependent on a few registries' policies, acquisition was the logical exit.

Stack. PHP + Node.js automation scripts, Bootstrap frontend, Stripe payments, IFTTT, multiple registrar accounts; no team, no funding.

Revenue 7/10 · Replicability 3/10 · Leverage 9/10 · Timeliness 6/10

Sources & confidence. Indie Hackers interview/podcast #034 (Mike Carson, 2016: 'I'm the only employee, annual revenue about to pass $1M') · Failory interview ($125K/mo, $99 price, launched June 2014, PHP/Node scripts) · GetLatka (2020: ~$1.5M ARR, 457 customers, $0 raised) · Domain Name Wire (Oct 2023 Dynadot acquisition, amount undisclosed, folded into DAX) · Hacker News (2016 post listing the business at $1.5M) — Medium — monthly revenue, margin, and exit timing are corroborated by the founder and multiple outlets, but the acquisition price is undisclosed and figures like ~70% margin and ~$150K/mo are interview estimates from years past, not audited.

Data & sources

Figures are drawn from founders’ public disclosures, media reports, Indie Hackers / Starter Story and similar public sources; "~", "est." and "undisclosed" are intentional. Full methodology and the complete source notes are in the main study.