Discussion of Key Uncertainties
OTA gave explicit consideration to several uncertainties in the decision analysis. These included uncertainty about ZIP+4 usage, multi-line OCR performance, single- and multi-line savings rate, multi-line OCR cost, single- to multi-line conversion cost, multi- line ZIP+4 use, national directory feasibility and cost, single/multi-line OCR obsolescence, and multi-line OCR procurement delay.
The ZIP+4 usage, multi-line performance, and single/multi-line savings rate have proven to be the most controversial uncertainties. These are discussed first, followed by the less controversial uncertainties.
As shown in figure 5, the three most controversial uncertainties were included in many of the decision options. ZIP+4 usage was treated as an uncertainty in analysis of options A, B, D, E, and, by extension, G and H. Multi-line OCR performance was treated as an uncertainty in analysis of options B, C, D, E, G, and H. The single/multi-line savings rate was treated as an uncertainty in options A, B, C, D, E, G, and H.
ZIP+4 Usage. USPS has based its analysis on the assumption that 90 percent ZIP+4 usage will be achieved by the end of 1988. The 90 percent is calculated as a percentage of total machinable, metered first class letter mail of about 51 billion pieces. In order to achieve 90 percent by 1988, USPS assumed the following interim usage rates: