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Factors 4
Chicago Population AI
millions
📊 World population ~8B — this value seems reasonable.
Fraction owning a piano
fraction
Avg pianos per owner
pianos
Tunings per piano per year
per year
Final Estimate
~102 piano tuners in Chicago
90% CI: ~20 – 200
Fraction owning a piano
65% 🔴
Chicago Population
22% 🟡
Avg pianos per owner
13%
History Page — `/history`

Your Past Estimates

How many piano tuners in Chicago?
~10² tuners · 90% CI: 20 – 200 · May 25, 2026
Total bytes sent over the internet in 2025?
~10²⁴ bytes · 90% CI: 10²³ – 10²⁵ · May 23, 2026
How many galaxies are visible to the naked eye?
~10⁴ galaxies · 90% CI: 5,000 – 10,000 · May 20, 2026
Cars in New York City?
~10⁶ cars · 90% CI: 500K – 2M · May 15, 2026
Library Page — `/library`

Your Factor Library

🎯 World Population
billions
Source: UN World Population Prospects 2024
Typical: 8.1B
💰 US GDP per capita
USD
Source: World Bank 2023
Typical: $65,000
🌡 Speed of light
km/s
Source: NIST fundamental constants
Typical: 299,792
📚 Books per library
volumes
Source: American Library Association
Typical: 100,000
🏠 Avg household size
people
Source: US Census Bureau 2023
Typical: 2.5
🍔 Calories per day, human
kcal/day
Source: WHO nutrition guidelines
Typical: 2,000
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Factors 3 Read-only
Chicago Population AI
millions
Fraction owning a piano
fraction
Avg pianos per owner
pianos
Final Estimate
~102 piano tuners in Chicago
90% CI: ~20 – 200
Fraction owning a piano
65% 🔴
Chicago Population
22% 🟡
Avg pianos per owner
13%