Increased competition among airlines means lower commission for travel agents. It used to be around 9%; currently it's unlikely that any airline will offer more than 7%..
It has to be remembered that the commission is paid to the agency, not to the individual employee who actually handled the sale. Most firms will only give a small part of the commisssion (if any) to the individual employee. Some firms might not directly pass any commission on. (e.g. they'll simply pay a basic salary, possibly with a periodic bonus based upon the total commission achieved by all employees in that firm, or at that particular branch).
Chris