The premise tells us that the shoe factory employs more unskilled full-time workers than all of the other businesses in Centerville combined. The conclusion then says that if the factory closes, more than half of Centerville's residents who are unskilled workers with full-time jobs in Centerville will lose their jobs.

At first glance, the conclusion seems to follow straightforwardly from the premise. If the factory has more unskilled full-time workers than every other business in town combined, wouldn't closing it necessarily leave more than half of those workers jobless?

But look more carefully at the conclusion. It doesn't say "more than half of the unskilled full-time workers in Centerville." It says more than half of Centerville's residentswho are unskilled full-time workers. That word "residents" makes a big difference. The premise tells us about workers employed by businesses in Centerville, but it doesn't tell us where those workers live. What if a significant number of the shoe factory's unskilled workers commute in from neighboring towns? They'd count toward the factory's impressive headcount in the premise, but they wouldn't count as part of the population described in the conclusion, because they aren't residents of Centerville.

If you want an example to understand this better, imagine the factory employs 100 unskilled full-time workers, and all other Centerville businesses combined employ 80. The premise is satisfied. But now suppose 60 of those 100 factory workers live outside Centerville. Only 40 factory workers are Centerville residents. Among the 80 workers at other businesses, suppose all 80 are residents. In that case, the relevant population of resident unskilled full-time workers is 120 (40 + 80), and the factory closing would only cost 40 of them their jobs, which is well under half. The conclusion would be false even though the premise is true.

So the argument needs to rule out this kind of scenario.

This doesn't feel like a typical Sufficient Assumption question where you're building a bridge between two concepts in a conditional chain. Instead, the gap is more subtle: it's about whether having more unskilled full-time workers than all other businesses combined implies having more unskilled residents who are full-time workers than all other businesses combined.

The cleanest way to guarantee the conclusion is to ensure that every unskilled full-time worker at the shoe factory is a Centerville resident.