With fewer vendors, influencing the market high. Goods and services can be substituted. Make each vendor wants to compete in the service to attract consumers.
The vendor has little influence on the market. Services can replace each other very well. Making individual vendors must do to compete in the service to attract consumers.
The seller the least amount of influence on the market is high. Products and services can be replaced as well. The seller must pay attention to the individual competition in service to attract consumers.