Project interdependencies pose a particular challenge in portfolio optimization. Such dependencies fall into two broad categories:
In this post, we only concern ourselves with hard dependencies. The wrench that foundation projects throw into a portfolio optimization effort is this: how do we prioritize projects that seem to provide little intrinsic benefit, yet are indispensable for “juicier” projects to be available? A simple examination of their benefit-to-cost ratio is clearly inadequate if by benefit we only mean their intrinsic benefit. But is there a possibility of simply redefining what benefit means for such foundation projects? Is it possible to somehow augment the benefit of these foundation projects with the benefit of the projects they enable? Unfortunately, the answer is no: things get more complicated in the presence of multiple dependencies. The following example gives us a window into why.
Consider the following mock portfolio. We simplify the presentation by reducing each project to two numbers: its benefit and its cost (we won’t go into the details of how we boiled down the benefit to a single value, here). An arrow represents a requirement: the project at the origin of the arrow is required for the project at the end of the arrow to be available.
The following table tells the story of what the optimal portfolio looks like for an increasingly higher budget. (The reader could easily verify this by hand.)
|
Total Cost |
Projects Funded |
Total Benefit |
Comment |
|
50 |
2 |
10 |
With that small a budget, only foundation project #2 can be funded, although it provides minimal benefit. In practice, one might elect not to fund it at allsince the portfolio B/C ratio is only .1. |
|
60 |
2+5 |
60 |
Small project #5, dependent upon foundation project #2, can now be funded. Notice that the combined B/C ratio is barely at breakeven now, i.e., equal to 1. |
|
110 |
1+2+5 |
65 |
A budget increment of 50 allows us to fund the second foundation project (#1), but the portfolio B/C ratio takes a hit again (.59). |
|
150 |
1+3 |
205 |
The availability of a budget of 150 makes project #3 with its intrinsic B/C ratio of 2 very appealing now. Here, we would sacrifice the 2+5 project combination (and its neutral combined B/C ratio of 1, as discussed above) to free the budget necessary to fund project #3. |
|
200 |
1+2+4 |
315 |
For an additional budget of 50, we can now fund both foundation projects and drop project #3 to instead fund the attractive project #4, which has the highest intrinsic B/C ratio of the set. |
|
210 |
1+2+4+5 |
365 |
Small project #5, again, nicely accommodates a small budget increment of 10, for an appealing incremental benefit. |
|
310 |
1+2+3+4+5 |
565 |
At this budget level, everything can be funded. |
This table showcases some of the subtleties associated with the valuation of a foundation project. If somebody were to ask, what is the “full benefit” of project #2 (not just its intrinsic benefit), the answer would be very different (if at all defensible) depending on the line we examine in this table.
At the heart of this difficulty lies the following fact: in the presence of dependencies no easy ranking method allows one to decide how or when to fund certain foundation projects. Instead, a full-blown optimization is required, taking into account the entire universe of projects. We have already discussed this topic in this previous post.
Folio Priority System automatically handles such complex dependencies in a seamless and user-friendly way.