Prior success rate
It is the average level of success among projects prior to current one, which each prior project weighted by link to focal project.
It tries to capture a new project's quality (how appealing to investors) through the quality of historical projects (e.g. by funding outcomes and other metrics).
Can be refined by regressing success onto other characteristics. This is because degree of success varies depending on goal and outcome. For example, a more conservative goal will be regarded with higher success if achieved at the same level as another project with a more ambitious goal.