Final answer:
The percentage of self-employed workers in the United States is closest to 6 percent, which includes individuals who own their own businesses and may include 'non-employer' business owners.
Step-by-step explanation:
The question about the share of self-employed workers in the United States pertains to contemporary labor market statistics.
According to the most recent data available, which is not explicitly provided in the given reference information but based on trends and external sources such as the U.S. Bureau of Labor Statistics (BLS), the percentage of self-employed workers in the U.S. is closest to the 6 percent (a) option rather than the higher values of 12 percent, 18 percent, or 24 percent.
This figure encompasses individuals running their own businesses, including 'non-employer' businesses where owners earn income without officially receiving wages or a salary.