• Methodology
• Updated Oct 17, 2026

How we count the trends

Every number on the Trends page is a count of public permit records. Here is exactly where they come from, how we sort them, and the rules that decide what we show.

Where the numbers come from

Each city's own open-data permit file, downloaded on a schedule and kept in a dated archive. We don't buy, scrape or estimate data, and we don't add records the city didn't publish.

Chicago data: this site uses data modified for use from its original source, www.cityofchicago.org; the City of Chicago makes no claims as to the content, accuracy, timeliness or completeness of the data. Marin County permit data: County of Marin, made available under the Open Database License (ODbL 1.0). Austin data: City of Austin Development Services Department.

Which date we use

Permits are counted by the date they were issued, except San Francisco, where we count the date the application was filed. Our San Francisco archive is kept by application date, so counting it by issue date would compare uneven windows. The Trends page labels San Francisco "applications filed."

How a permit gets a category

We read the work description each city wrote on its permits and sort them by the kind of work they describe. Where a city keeps its own category for the same thing, we use the city's category. We sort conservatively: when a description is unclear, we leave the permit out rather than risk counting it wrong.

• EV chargers: Permits whose record mentions EV chargers or charging stations.
• Solar: Permits whose record mentions solar or photovoltaic (PV) systems.
• Battery storage: Permits whose record mentions battery or energy storage.
• Heat pumps: Permits whose record mentions heat pumps or mini-splits.
• ADUs: Permits whose record mentions an accessory dwelling unit (ADU).
• Restaurant build-outs: Permits whose record mentions a restaurant, café, bakery, brewery or commercial kitchen work.

A permit can be in more than one category (solar with a battery, for example). Counts are permits, not projects: one project can have several permits.

The rules for what we show

• Each place against its own past. Cities count permits differently, so we never rank one city's raw count against another's.
• Complete months only. A quarter is shown only once every source's data runs past its last day.
• Too few to compare. With fewer than 20 permits in the earlier period, we show the counts and no percentage.
• Big moves. A change of 50% or more is marked "we don't know why yet" until the records explain it. We don't guess at causes.
• Missing wording. If a city leaves the work description blank on more than 20% of permits in either period, we don't compare categories that depend on it. Marin County stopped publishing descriptions in early 2026.
• Terms first. A source appears only after we've read and recorded its terms of use. Los Angeles is held back while we confirm its terms.
• Full history only. San José's public file keeps active permits only, so finished permits drop out and a year-over-year count would be wrong. It isn't shown.
• Area counts only. No addresses, owners or names appear on the Trends page.

What these numbers are not

They aren't forecasts, rankings, investment advice or a measure of dollars spent. A permit is planned work; it doesn't guarantee a project happens. We report what the record says.

Corrections

Every count can be checked against our dated archive of the city's own file. If you think a number is wrong, email roger@pickersdesk.com with the city and category. If we made the error, we fix it and note the change. If the city's record changed, we say so and link the official source.

See how complete and current each source is on the data report card.