At larger firms with 100 or more employees, nearly half the billings in 2018 were from projects billed with a stipulated sum (fixed fee). The second largest share of firm billings (28 percent) were billed using a professional fee plus reimbursables. For smaller firms, the largest share of billings were from projects billed using an hourly rate. However, use of hourly billing has trended down over the last few years. Billing projects based on percentage of construction costs has trended upward during the same time period.
Source: AIA’s 2019 Business of Architecture Report