What type of cost estimating can be most effective at the beginning stages of developing new systems with no historical data?

Estimating by analogy is particularly effective during the early stages of developing new systems when historical data is limited or unavailable. This method relies on comparing the new project to similar previous projects. By analyzing the costs incurred in those analogous projects, estimators can extrapolate potential costs for the new system, making adjustments based on differences in scope, complexity, or scale.

In situations where historical data isn't present, estimating by analogy allows for a rough but informed estimate rooted in tangible experiences from similar endeavors, providing a starting point for project budgeting and planning. It harnesses the value of previous findings without needing detailed metrics specific to the new system under consideration.

Other methods such as parametric estimating, while useful, typically rely more on statistical relationships derived from historical data. Direct engineering and manufacturing estimates demand detailed knowledge of the project's specifics and often cannot be effectively applied without prior data. The Delphi technique focuses on gathering expert opinions through iterative rounds of questioning, which can also be useful but does not provide a direct analog comparison to draw cost estimates from.

Thus, estimating by analogy stands out in the context of limited historical data, allowing for practical decision-making in the early stages of project development.