Multi-person firms are rated per person per 6 months or 12 months and rated by commission level (greater or less than $20,000 per policy period, for instance). The idea is that someone with less commission is working less, has fewer transctions and creates less exposure.
Some companies that franchise, such as C21 or Tarbell, may have a completely different system, such as one where agents buy in to a master policy every 6 or 12 months. Check with your broker for details.