Dear Subhendu,
CTC is a conceptual projection of the total or overall cost of employment per employee in a year adopted by industries in certain countries like India and South Africa. Basically, it is variable depending upon many factors like the nature of the job performed by the employee, place of work, gender, incidental expenses incurred and reimbursed, types and extent of fringe benefits, and the like.
For example, if the office is located in a prime commercial location, even the proportionate rental value of the cubicle occupied by the employee is included in the CTC by some companies. Some companies include the cost of periodic training for updating knowledge and enhancing employment skills of their employees in the CTC.
Therefore, at best, it is an accounting formula to assess the overall cost per employee from the employer's perspective only and serves to lure job-seekers in the employment market. A higher CTC need not necessarily ensure a higher take-home pay, nor can it be a realistic monetary value of labor from the employee's perspective.
As far as I know, the Government never adopts the CTC concept in its own wage and salary administration policies or in the matter of fixation and revision of statutory minimum wages applicable to scheduled employments. Therefore, there is no scope for devising a straight-jacket formula of component-wise percentage in the wage/salary structure of employees to their CTC. It is a matter left to the discretion and bargaining power of the individual employer and employees.