EEIO
EEIO (Environmentally Extended Input-Output) is an economic modeling approach that estimates greenhouse gas emissions per dollar of economic output by industry sector, commonly used for Scope 3 spend-based emissions calculations.
EEIO models use national economic input-output tables combined with environmental satellite accounts to produce emission factors expressed in kg CO₂e per dollar spent, broken down by industry sector. The US EPA publishes the USEEIO model, which is the most commonly used source for spend-based emission factors in North American carbon accounting.
Spend-based emission factors are the fastest way to estimate Scope 3 Category 1 (Purchased Goods and Services) when supplier-specific data is unavailable. The process works by mapping each line of spend data to an industry sector (typically via NAICS codes) and applying the corresponding EEIO factor.
When using spend-based factors, inflation and foreign exchange adjustments are important because the emission factor was developed for a specific dollar year. Gravity automatically applies BEA industry-specific price indices for inflation adjustment and currency conversion so that the spend data is compared in consistent dollar-year terms.
While EEIO-based estimates are the lowest-quality tier in the data quality hierarchy, they provide a defensible starting point that organizations can improve over time by engaging suppliers for activity-based or supplier-specific data.
Frequently asked questions
When should I use EEIO-based factors versus activity-based data? +
EEIO (spend-based) factors are the fastest starting point for Scope 3 when supplier-specific data is unavailable. They provide defensible estimates that can be progressively upgraded as you engage suppliers for activity-based data, which is higher quality and more accurate.
Related terms
Emission Factor
An emission factor is a coefficient that converts an activity measurement — such as litres of fuel burned, kilowatt-hours of electricity consumed, or dollars spent on a commodity — into a quantity of greenhouse gas emissions, typically expressed in kilograms or tonnes of CO₂ equivalent (tCO₂e).
Scope 3 Emissions
Scope 3 emissions are all indirect greenhouse gas emissions that occur in an organization's value chain — both upstream (suppliers, purchased goods, business travel, employee commuting) and downstream (product use, end-of-life treatment, investments). Scope 3 typically represents 70–90% of a company's total carbon footprint.
Emission Factor Rules
Emission factor rules are saved instructions in carbon accounting platforms that automate which emission factor is applied when certain conditions are met, turning expert factor decisions into reusable, auditable logic.