The hosting boom is bigger than the data-centre count.

St. Charles has the concentration. Fairfax has the larger gain.

St. Charles County, Missouri has 350.53 hosting jobs per 10,000 private jobs, the highest reportable rate. Its 4,958 hosting jobs sit within a private employment base of 141,442.

Fairfax County, Virginia has a lower concentration, 299.68 per 10,000, but a larger hosting workforce of 16,122. Its recorded gain of 10,035.7 quarterly-average jobs compares with 1,800 in St. Charles. The county leading one measure need not lead the other.

The gap between the two measures can come from at least three things: a small specialist economy can produce a high rate while producing few jobs; a large county can absorb a major gain with less visible change in its mix; and employment can move between registered locations without either place adding a job.

We'd ask both questions before crediting a policy, but neither answer alone tells us whether policy worked.

A spectacular percentage can begin with a small workforce.

St. Joseph County, Indiana grew from 121.7 to 1,233 quarterly-average hosting jobs, an increase of 913.4%. It leads the eligible percentage-growth ranking, while placing 16 on concentration.

We'd keep that starting count in the headline.

Our growth ranks require at least 100 jobs in the base quarter. That's a safeguard against tiny bases, not a reason to stop looking at them. St. Joseph's gain is substantial, but the percentage alone can't tell a reader the scale of the workforce.

We also found a national gap: registered hosting establishments grew 122.68%, from 25,139 to 55,979, while jobs grew 46.46%. This is consistent with smaller operating units, but the record alone cannot prove that.

It could also include contractors or affiliates registering separately, reporting changes after reorganisations, or more sites with similar total staff.