Both these questions keep coming up again and again as IT managers are forced to justify staffing and budgets. I do not work in the financial services industry, but I don't think that really matters in this case.
The short answer to both is thatthere is no magic (or even average) staffing ratio, and trying to determine a budget as a ratio of earnings is of absolutely no use.
Staffing: The size of the IT staff should be based on a number of factors. Some of these are: age and complexity of hardware supported, age and complexity of software supported, technical knowledge and capabilities of users, presence of in-house development projects, services provided, and of course,the size of the user base. Trying to determine staffing levels based on an single factor will not work. You will either end up with a small overworked staff that continuously works 75-hour weeks just trying to catch up, or you will end up with a large staff that spends most of its time playing games.
Budget: Telling you that a budget should be a certain percentage of annual revenues makes absolutely no sense. If I tell you my IT budget is 5 percent of revenues, you may accept that without question as being reasonable. However, I have told you nothing unless you know what my company's revenues are and the size of the work force supported. If I tell you we have $10 million in annual revenue and I support 100 people, 5 percent probably doesn't make sense ($10 mil * 5 percent = $500K)! If I tell you my department supports 900 people in 17 locations, it still doesn't make much sense, so percentages of revenue really mean nothing. When preparing a budget you must factor in the knowns: salaries, services, and mainenance. Then you must factor in planned growth: new staff, new equipment, new locations, upgrades to equipment/software. Then add a contingency factor to (hopefully) handle any emergencies/unknowns.
