Large projects can involve highly complex financial plans and often start with a conceptual estimate performed by a building estimator. As portions of a project are completed, they may be sold, supplanting one lender or owner for another, while the logistical requirements of having the right trades and materials available for each stage of the building construction project carries forward. Public–private partnerships (PPPs) or private finance initiatives (PFIs) may also be used to help delivery major projects. According to McKinsey in 2019, the "vast majority of large construction projects go over budget and take 20% longer than expected".