Current data indicate that PPPs often can result in significant project cost and time savings compared to traditional procurement. Causes can include direct incentives to the private contractor for on-time delivery; use of warranties (see Glossary) or performance-based contracting; competition among bidders; transfer of risk to the private sector for cost and schedule overruns or revenue shortfalls; and lifecycle efficiencies (see below).35 Some private contractors, however, may lower their costs by cutting staff, hiring non-union employees, or reducing pay and benefits, which could raise labor-related concerns (see Labor Concerns on pages 12 to 13).