Using the treemap data visualization technique to study the likelihood of cost overruns from bidding data

The treemap data visualization technique is applied to highway construction bidding for over 300 projects from the State of California in an effort to find factors that make a project more likely to have cost overruns. Factors studied included the number of bids, the number of project line items, the concentration of project cost in the largest costing line item and a measure of the dissonance between bidders. The treemap analysis indicated that projects with a low number of bidders signified that project cost overruns were more likely. Also, projects whose costs were dominantly concentrated on one single line item tended to have lower costs overruns as compared to projects whose costs were equally spread among all the line items.