Final answer:
Specific percentage breakdowns between bootstrapped and investor-funded small businesses under 50 employees are not provided, but evidence suggests a significant portion of these are likely bootstrapped due to their size and structure.
Step-by-step explanation:
The question seeks to understand the percentage breakdown between bootstrapped (self-funded) and investor-funded small businesses in the United States, particularly those with fewer than 50 employees. Although specific percentage figures are not provided, we can infer that a significant portion of small businesses are bootstrapped, considering that the vast majority of American firms have fewer than 20 employees and are likely to fall into the category of small "non-employer" or privately-owned entities.
These small entities often do not have formal salaries but rather earn income directly from business profits, suggesting that many of them are likely self-funded, at least initially. Moreover, the U.S. Small Business Administration indicates high levels of business turnover, with many small firms entering and exiting the market annually, which implies that a mix of bootstrapping and external investment could be present among these small enterprises.