Figure 1 illustrates the model. The basis of this model is a definition of demand in economics, stating that demand is the number of goods or services that a consumer wishes for and can buy in a certain period of time (
27). In this model, the types of flows were headcounts. The boxes that were not headcount type were named influential factors (i.e., the factors that affect individuals’ health, needs, and demands), which will exert their influence on the model through rates. These rates either exist or can be estimated.
The need-adjusted demand model
The first main column in the model is related to population and demographic changes. The second column is related to the population in need of services. In this study, the needs are divided into three categories by the researchers, namely acute and mild, acute and severe, and chronic diseases. Each category has a rate, and by multiplying the rate by the number of the population at any time, the number of individuals who need each category of services will be identified.
According to the definition, acute and mild diseases refer to those conditions that are mostly treated with self-care and mostly require outpatient care services. Acute and severe diseases are those conditions that require prehospital emergency services, hospital emergency, or hospitalization in the emergency department (under observation emergency). Chronic diseases are those conditions for which an individual receives mainly specialized and sometimes general inpatient or outpatient services.
The rates of this part of the model are affected by the demographic and epidemiological transition. Demographic transition is caused by the age pyramid, healthy lifestyle behavior, and social health determinant factors. The epidemiological transition has an effect on genetic, behavioral, and environmental risk factors.
After determining potential needs, for converting to demand according to the definition that it presented at the beginning of the Results section, the next step (i.e., the third column) is to convert the needs into the willingness to receive services by willingness rate; accordingly, there are a number of potential needs, and the individual has a willingness to receive services. The transformation of potential needs into willingness is influenced by general literacy. General literacy results from a number of factors, including health literacy, self-care behavior, health service provider-induced demand, and direct-to-consumer advertising.
After the determination of need and willingness in individuals, the discussion of ability is raised. The rate of ability is influenced by three main components, including availability, physical accessibility, and affordability. Finally, using the ability rate, the number of individuals who need health services and are willing and able to use them will be determined. The number of medical centers is effective in availability. The geographical distribution of medical centers has an effect on physical access. Moreover, some factors, such as the type of insurance coverage and the economic status of families, have an effect on affordability. The economic status of families is a function of gross domestic product, economic growth or recession, and inflation or other factors that are introduced under this general term and affect affordability.
In the next step, it is important at what rate and what type of specialist an individual who has a need is willing and able to refer. Acute and mild patients who are willing and able to refer to health service centers might refer to complementary, alternative, and traditional medicine centers or refer to general or specialized outpatient service centers with separate rates. Acute and severe patients willing and able to refer to health service centers might refer to general or specialized outpatient service centers and emergency or inpatient service centers with separate rates. Chronic patients willing and able to refer to health service centers might refer to complementary, alternative, and traditional medicine centers, general or specialized outpatient service centers, or inpatient service centers with separate rates.
The rates determine the number of individuals who need, wish for, and are able to use health services according to the number of individuals referring to each type of service. Numerous factors affect the rates of this part, including health-seeking behaviors, the structure of the health service delivery system, managed care, and differences in tariffs for services.
Since, in the end, the final product in the need-adjusted with demand model should be the type of headcount, by using the conversion coefficient of referrals to the full-time equivalents of physicians based on national standards, the number of referrals would be converted to the number of full-time functional equivalents required by physicians in the health market of the country. This coefficient can be the number of patients that a physician visits per day or something similar based on national standards or the opinion of experts.