Source: MITRE, Ada in the Maintenance Arena

From the Script: SLIDE 12 - Ada in Maintenance Arena

Where Ada cost savings are most apparent is in maintenance of large, complex software programs.

In the mid-1970's, while working at IBM, Allan J. Albrecht developed the function point analysis method, the most accurate and reliable method for estimating time and cost of a systems engineering project. It measures the system's logical process characteristics, such as the number and complexity of its internal logical files and its external inputs and outputs. [Davis]

The results of a MITRE study show that, by function point, Ada maintenance is much less costly than other higher-order languages, and significantly less costly than C. [Shrank, p. 4]

C has a long way to go even to reach parity with Ada: a 100% increase in productivity and a 50% increase in quality would not reduce the cost of C to that of Ada.