Great question, Norris.
I recommend you connect with the folks as the Tax Foundation. Although not specifically focused on small businesses, an analysis they put out in 2019 indicates the U.S. businesses remit 93% of all taxes collected.. Of this, 64.2% are payroll and consumption taxes paid by businesses on behalf of employees and consumers, with 28.9% are direct taxes paid by businesses.
https://taxfoundation.org/data/all/federal/businesses-pay-remit-93-percent-of-taxes-in-america/
Some addition things you probably want to consider:
1. How are you going to define small business?
2. Does your definition include self-employed / sole propriotors?
3. What taxes do you want to count (administrative level, tax type)?
These are more questions than answers, but as you indicated, this is not a simple question.
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Daniel L. Bennett
Cobb Family Chair in Entrepreneurship
College of Business
University of Louisville
Daniel.Bennett.2@Louisville.edu------------------------------