Experts estimate that insurance companies' tardiness in paying doctors for legitimate medical claims adds approximately 10 percent in overhead costs for physicians. Insurance companies counter that the tardiness sometimes results from billing errors made by the doctors themselves. Since dealing with these billing errors costs the insurance companies time and money, it is clear that insurance companies do not have a significant economic incentive to delay claim payments to doctors.

Which of the following pieces of information, if true, weakens the conclusion above?
Some doctors who submit accurate bills to insurance companies still receive tardy payments.
The cost to the insurance companies to process incorrect bills from doctors' offices is roughly equivalent to the increased costs that physicians accrue as a result of tardy payments from insurance companies.
A rising proportion of medical claims submitted by doctors to insurance companies are deemed illegitimate by those insurance companies.
The billing errors made by doctors' offices are typically very minor, such as the submission of a claim with an outdated patient home address.
The overhead costs incurred by doctors as a result of delayed insurance payments result in an increase in the premiums paid by consumers to health insurance companies that far exceeds any increase in the fees paid to doctors by insurance companies.