The concept of "fairness" that I talked about in my previous post applies here. If two companies submit proposals in response to an RFP seeking to acquire 1,000 Widgets and Company A responds with a price of $10,000 while Company B responds with a price of $20,000, the government is required to chose Company A because they are cheaper. However, if Company B is a small business/minority-owned business/service-disabled-veteran-owned-business/etc, the contracting officer can choose Company B because it fulfills other requirements to support those types of businesses.

I could see some small cases where the government would restrict the size of the company responding to an RFP, but there are also ways around that. The small business can contact the contracting office and protest saying they were unfairly considered for that acquisition and usually will win.

The key to the Federal Acquisition Regulations (FAR) is that they try in earnest to support and encourage fairness when awarding contracts. Furthermore, the government goes out of its way to give the "underdog" a better-than-equal chance at winning the contract.

As another poster said, the small business can't lose out on other reasons (i.e. certifications, financials, etc). It could be that they're losing contracts for very different reasons.

Here are some links for reference:

SBA size standards: https://www.sba.gov/content/small-business-size-standards

GSA Small businesses: http://www.gsa.gov/portal/content/202261

Small business set asides: https://www.acquisition.gov/?q=browse/far/19/5&searchTerms=s...

Protests: https://www.acquisition.gov/sites/default/files/current/far/...