How Mainline knows what it claims to know.

The Live Index is the five-row data block on the homepage. It tracks headline indicators we believe operators should glance at the way a trader glances at S&P futures: cheap context, fast.

• U.S. SMBs. Total count of US businesses with under 500 employees, derived from the most recent U.S. Census Bureau Statistics of US Businesses release. Updated quarterly as Census revises.
• Median local svc. margin. Median operating margin across the local-service verticals we cover (plumbing, HVAC, electrical, dental, vet, auto repair, landscape, cleaning, restaurants). Drawn from a panel of ~1,200 operators who share aggregated P&L data — currently in pilot.
• HVAC techs / 10k pop. Bureau of Labor Statistics Occupational Employment and Wage Statistics series, SOC code 49-9021 (HVAC mechanics and installers), normalized to population from the most recent Census ACS 5-year estimates.
• Avg dental cleaning, US. National median fee for a single adult prophylaxis (ADA code D1110). Sourced from the American Dental Association Survey of Dental Fees, supplemented with our panel of dental-practice operators.
• Restaurant 1yr survival. SBA Office of Advocacy birth-and-death-of-firms data, filtered to NAICS 722 (food services and drinking places).

Mainline draws on five families of source data. Every figure we publish should map cleanly to at least one of these. If a figure on the site is missing its source attribution and you need one, email corrections@themainline.site — we publish the trace.

• U.S. Bureau of Labor Statistics (BLS). Wage data, employment by industry, occupational outlook. The authoritative US labor source. bls.gov
• U.S. Census Bureau / SBA Office of Advocacy. Business counts, geographic distribution, firm-formation and dissolution velocity. Statistics of US Businesses (SUSB) and Business Dynamics Statistics (BDS).
• State business filings. Aggregated incorporation and dissolution records from the 50 state secretaries of state. Useful for leading-indicator counts that beat federal release cycles by 2–4 quarters.
• Public review aggregators. Google Business Profile, Yelp, Angi, BBB, Birdeye, and industry-specific equivalents (Houzz for trades, Healthgrades for medical). Used for review-volume and sentiment-theme analysis — never for individual identification or attribution beyond what each platform makes public.
• Industry trade associations. Vertical-specific benchmarks: ACCA (HVAC), NRA (restaurants), ADA (dental), AVMA (vet), NALP (landscape), NFIB (cross-sector small business). We cite the trade group on every figure drawn from their work.
• The Mainline panel. An operator-survey panel currently in pilot, bootstrapped from (a) aggregated tool-usage signals from operators who have opted in via The Stack and The Lab, and (b) direct survey responses from subscribers. As of May 15, 2026, the panel represents roughly 1,200 operators across the verticals we cover. We are working toward a public methodology document for the panel; until that ships, we tag panel-derived figures explicitly so readers can apply their own discount.

Specific derivations behind the Live Index, in plain English:

• U.S. SMBs (33.3M). SUSB count of employer firms with under 500 employees, plus SBA non-employer firm count. Includes sole proprietorships, which is the relevant universe for our coverage.
• Median local service margin (14.6%). Panel-weighted median of operating margin (revenue−COGS−operating expenses) / revenue across our 9 vertical buckets. The trailing-12-months figure is updated monthly as panel data refreshes.
• HVAC techs per 10k (3.8). National BLS estimate of 442,000 HVAC techs ÷ US population of 334M × 10,000. Both numerator and denominator updated annually.
• Avg dental cleaning ($127). ADA Survey of Dental Fees national-median figure for D1110, cross-checked against our dental panel (n=190). Year-over-year change is the official ADA figure.
• Restaurant 1-year survival (80%). SBA Business Dynamics Statistics survival rate for NAICS 722 firms born in the most recent complete cohort year. Year-over- year delta is reported in percentage points.

• Mainline is not financial advice. We don't make buy/sell recommendations on specific businesses or franchises.
• Our pricing signals are observational, not prescriptive. Whether a price increase is appropriate for your specific market depends on factors we don't see from the outside.
• Individual market conditions vary — sometimes wildly. A statewide median is a starting point, not a forecast for your county.
• We are not lawyers, accountants, or tax advisors. Where regulation matters (refrigerant transitions, labor classification, etc.), confirm with a professional in your jurisdiction.

If a number on Mainline is wrong, we want to know. Email corrections@themainline.site with the figure, the URL, and what you believe the correct value is. We respond within 5 business days.

Material corrections — anything that changes a Live Index figure or a published number in The Wire — are published with a dated changelog on this page, alongside a footnote on the original source where the wrong figure appeared. We don't quietly edit history.

v1 — May 15, 2026 — Initial publication. Live Index methodology and source list documented.