Success Case #1: Cost Efficiency
Figure 1. Cost Efficiency
To compare the cost efficiencies of numerous projects, we need to minimize the effects of varying labor rates. To that end, we viewed cost through the lens of effort hours expended (i.e., cost = effort * labor rate). Using this method, we can see that agile projects with fewer than thirty thousand source lines of code, or SLOC, are less costly than similarly sized nonagile projects. The trend seems to reverse itself in projects above the thirty thousand SLOC threshold, but in a subtle way.
The larger agile projects are fairly closely clustered; that is, for a particular size, there is not much variation in effort and cost. The larger nonagile projects, however, are either much less costly than their agile counterparts or quite a bit more costly. On average, large agile projects are a bit more costly, and this disparity seems to increase with size.
In fact, what seems most apparent in this analysis is that both agile and nonagile projects realize the greatest cost and resource efficiency benefits when packaging up delivered features into small releases with fewer than thirty thousand SLOC.
Bottom line: The agile cost advantage phases out at around thirty thousand SLOC. Above that threshold, agile projects may actually be more costly than traditional waterfall projects. If cost efficiency is your primary concern, both agile and nonagile projects should keep release sizes small.
Success Case #2: Schedule Efficiency
Figure 2. Schedule Efficiency
Our schedule analysis shows that time to market is consistently shorter for agile IT projects, but that agile schedule edge diminishes as the volume of delivered features increases.
Bottom line: If schedule is your primary concern, large agile projects are consistently more time-efficient than similarly sized nonagile projects, but the agile schedule advantage diminishes as project size grows.
Success Case #3: Balanced Productivity
Figure 3. Balanced Productivity
To evaluate balanced schedule and cost productivity, we looked at a metric called the productivity index, or PI, which—unlike traditional productivity measures that examine resource or schedule efficiency, but not both—takes both time and cost into account.
According to the data, larger agile projects enjoy a modest productivity edge over nonagile projects, but again, the effect is quite subtle.