“What is the typical ratio of HR people to employees in an organization?”
At this point in time the number is close to 150 employees for every HR person. That being said the numbers don’t really tell the whole story. Case in point is the average company gets their first full-time HR person by the time they hit 100. It may be that they don’t add the second until they hit 300, driving the 150 average home. Overall you need to consider how much consistent activity around HR activities exist including hiring and turnover.