We do not use census data, because they are extremely outdated. It's part of the reason we can make accurate predictions before other companies can, since they do look at census data.
We use alternative data, which has recently become popular in the finance industry. For example, if you ask executives at a big company what their profit outlook is, they will always be optimistic, otherwise, their stock might decline and they may panic the market.
If you waited until the quarterly announcement, then you would be finding out at the same time as everyone else, and it's delayed information.
However, some people have found that you can more accurately predict a company's outlook on their quarterly performance by monitoring job boards and see how many open positions the company is hiring for. This allows people to gain insight and act before the rest of the market catches on.
We use the same approach but for real estate. For example, if you monitor the number of french bull dogs in a neighborhood, you can accurate predict median income values for that neighborhood before any official statistics. This is because those dogs are very expensive, so someone willing and able to spend a few thousand dollars on a pet tend to have a higher economic background.
We do use some paid sources such as satellite imagery and some data sources require you to pay for their api like our weather data vendor.