In systems based on salary it is common practice to express the pension as a specified proportion (e.g., of pensionable salary for each year of service, subject to a maximum (e.g., forty sixtieths). There are numerous methods of defining pensionable salary, the most popular being probably the terminal salary, i.e., that earned in the last year before retirement or, in order to avoid fortuitous inequalities of treatment, the average of the last few years of service. Another plan often adopted is to take the average salary throughout service. Where the employee contributes a fixed percentage of his salary throughout his service, and the employer makes annual payments equal to the aggregate contributions made by his staff, it has been argued that from the standpoint of equity the resulting pension should be related to the contributions which have been paid by, or on behalf of, the beneficiary and that accordingly the average salary method should be adopted. But a practical objection to this is that the pension based on average salary is likely to be insufficient to enable a senior officer to maintain a reasonable standard of comfort after retirement unless the scale is fixed so high as to be over-generous to the lower-paid ranks. In this connection it has to be remem bered that while all new entrants, with trifling exceptions, start in junior grades entitled to low salaries, their progress varies widely. Judged on the principle that an official, retiring after long service, ought to be able to maintain approximately the style of living to which he has been accustomed, anomalies appear inevit able under the average salary system, and for this reason the terminal salary system has become increasingly popular. With regard to the contention that the average salary system is fairer to the lower paid grades, it may be said that as one of the main objects of an employer is to secure efficiency his contributions may fairly be allocated in the best way to achieve this purpose; and it is generally agreed that since even under the terminal salary method the employee, whatever his rank, receives at least full value for his own contributions and some part of the employer's subvention, the unequal distribution of the latter is not a valid criticism of the fairness of the scheme viewed as a whole.
The average salary system approximates more nearly to giving each employee the equivalent of his own contributions increased proportionately out of the employer's grant, but if exact equiva lence is desired the scheme has to be framed on other lines. In such a case each contribution secures a definite amount of de ferred pension, varying with the amount of the contribution, the age of the employee and the age at which the pension is to com mence. On retirement instalments of pension purchased through out service are aggregated. The system, generally known as the "money purchase" plan, is easy to work and is often adopted, especially in America and where it is found convenient to re-insure the liabilities for pension with an assurance company in lieu of instituting a private superannuation fund.