1) the level of individual officer's efficiency in terms of knowledge & skills etc;
2) the industrial relations climate. If peaceful, it saves lot of time of HR dept. If complex, it consumes lot of time to deal with issues. .;
3) the load of daily work - whether the HR department looks after only HR work but also has to discharge administrative work like house keeping etc;
4) the amount of court cases; attending courts and preparing replies take lot of time;
5) the soundness of systems and methods of working in place;a well defined system brings clarity to the method of working;
6) the level of computerization of processes.
7) the load of statutory compliances
8) the rate of employee turn over a sit compels teh organisation to recruit employees time and again and attend to F&F settlements.etc.
Thus it all depends up on the above factors. accordingly yu need to plan the requirement