For office accommodation the unit is 1,000 letters posted or delivered, whichever is the greater number at the office in question. Certain ratios are taken for the expression in terms of letters of the various divisions into which the work performed by the post office falls. As between letters and parcels the ratios are as follow:-- UNITS RATIOS. -------------------------------------------------------- | VALUE IN LETTERS. +----------------------------------------- | Indoor | Outdoor | Office | Work. | Work. | Accommodation. --------------+--------+---------+----------------------- Letter posted | 3/5 | -- } | { 1 (whichever is the " delivered | 2/5 | 1 } | { greater traffic) " forwarded | 1/3 | -- | 1/2 " collected | -- | x | -- | | | Parcel posted | 6 | -- | 6 " delivered | 6 | 10 | 6 " forwarded | 4 | -- | 6 " collected | -- | 10x | -- --------------+--------+---------+----------------------- 1,000 letters (weekly) = 1 unit of postal work. For each unit of work so determined there is a corresponding normal cost. For indoor work the normal cost is approximately £15, for outdoor work £22 10s., and for office accommodation £2 10s., per annum. Since the unit to which a certain normal cost is allowed is built upon calculations which give a parcel a definite relative value as compared with a letter, the ratios show the relative cost to the Post Office of a letter and of a parcel. TABLE E RELATIVE COST OF STAFF FOR LETTERS AND PARCELS. It is estimated that on the average more than half the total number of letters are not sent forward direct to the post office of destination, but are forwarded from the office at which they are posted to an intermediate office; that is to say, more than half the total number of letters travel in two mails, and incur a handling at an intermediate office. The handling at that office is termed "forwarding." The letters are termed "forward letters."[630] Expressed in another way, the estimate is that all letters are forwarded, on the average, in 1.6 mails. It is estimated that on the average a greater proportion of parcels travel in this way in two mails. The actual estimate is that a parcel travels in 1.8 mails. Hence-- Total handling of 1 letter = 1 letter posted + 1 letter delivered + 0.6 letter forwarded. Total handling of 1 parcel = 1 parcel posted + 1 parcel delivered + 0.8 parcel forwarded. Now a letter forwarded = 1/3 letter posted and delivered (Table D). And a parcel forwarded = 1/3 parcel posted and delivered (Table D). Hence total handling of 1 letter = 1.2 letter posted and delivered. And total handling of 1 parcel = 1.26 parcel posted and delivered.