To counter the effects of adverse selection, insurers may offer premiums that are proportional to a customer's risk by distinguishing high-risk individuals from low-risk individuals. For instance, medical insurance companies ask a range of questions and may request medical or other reports on individuals who apply to buy insurance. The premium can be varied accordingly and any unreasonably high-risk individuals are rejected ("cf." pre-existing condition). This risk selection process is part of underwriting. In many countries, insurance law incorporates an "utmost good faith" or "uberrima fides" doctrine, which requires potential customers to answer any questions asked by the insurer fully and honestly. Dishonesty may be met with refusals to pay claims.