The phrase "are a substantial factor of" is correct and usable in written English.
It can be used when discussing the importance or influence of something in a particular context, often in academic or analytical writing.
Example: "The economic policies implemented by the government are a substantial factor of the country's growth."
Alternatives: "are a significant contributor to" or "play a major role in".
Although high bed occupancy has a number of causes, delayed discharges through shortfalls in social care are a substantial factor.
I'm not entirely sure where I'm going here, so to drag it back: toughness, is that something that only really "sells" in indie games, and has it been a substantial factor in some of the best titles on the market these past few years?
To prove liability in a tort case, plaintiffs must show asbestos was a "substantial factor" in the chain of causation.
On December 17 , 2009 Judge Forester granted a passenger family's motion for "partial summary judgment" determining, as a matter of law, that Comair's flight crew was negligent, and that this negligence was a substantial factor causing the crash of Flight 5191.
Aging is a substantial factor in the development of breast cancer.
The cell invasiveness of Mycoplasma gallisepticum, the causative agent of respiratory disease in chickens and infectious sinusitis in turkeys, may be a substantial factor in the well-known chronicity of these diseases and in the systemic spread of infection.
The question addressed in number three was whether, even if the proper warning had been placed on the product, such warning would have been a substantial factor in preventing Graves' consumption of it, and the resulting harm.
Colocation, or the ganging of several carriers on one tower, consolidates the environmental impact and increases the rental income, which can be a substantial factor.
The jury said Propulsid, which was removed from the market in 2000 after being linked to 70 deaths, was not a substantial factor in the death of John Calvert of Napa, Calif.
Platelets are the first cells reaching the injury site and are a substantial reservoir of critical growth factors and signaling molecules, including leukocyte-derived catabolic cytokines and fibrinogen.
