100 Isn’t a Magic Number, So Why Is It Part of the Vaccine Mandate?

The threshold of 100 employees adds to a patchwork of small-business rules. It shows up in no other major small-business laws. The reasoning behind the number is a mystery.

When the Biden administration announced an upcoming mandate that employees be vaccinated or tested regularly at companies with 100 or more employees, business leaders responded with a barrage of questions. Among smaller companies, one loomed especially large: Why 100?

It’s an appealingly round, easy-to-remember number, and it captures a broad swath of the American work force. President Biden estimated that his order would apply to 80 million employees and cover two-thirds of all workers.

But as a dividing line between a “big” business and a “small” one, it’s a threshold not found in any other major federal or state law. There was no explanation for how or why the number was chosen. And for entrepreneurs who employ a smattering of workers, that’s an increasingly common challenge: Every time lawmakers invent a new regulation, they also make up a new definition of which businesses count as small.