system
Given the following post, respond as if you're commenting on Reddit:
human
How are demand curves empirically estimated in practice?

How can we hold consumer tastes constant in a regression model? What is the most practical way to estimate a market demand curve for a particular product?

I'm very interested in hearing personal experiences with regards to this (if anyone has had any, that is). Feel free to go into detail when it comes to invoking statistics.
gpt
One of two ways:

1. You are the firm selling that product and do small price experiments. 
2. You use observational data and use instrumental variables as random quasi-experiments. That is, you want to get data on some variables that affect the supply of the product but not the demand (e.g., cost shocks). Then you use two stage ordinary least squares. There are more sophisticated methods that take lots of things into account. For example, you can also use structural multinomial choice models, adjust for measurement error, include random coefficients, and so on. But any method that you use will require instrumental variables that shift supply without affecting demand.