As with any activity thought to improve health, researchers are trying to identify the specific characteristics of volunteering that provide the greatest benefit. For example, how much time would you need to put into volunteer work to lower your blood pressure or live longer? In the Carnegie Mellon study, 200 hours of volunteering per year correlated to lower blood pressure. Other studies have found a health benefit from as little as 100 hours of volunteering a year. Which types of volunteer activities improve health the most? No one really knows. Sneed speculates that mentally stimulating activities, like tutoring or reading, might be helpful for maintaining memory and thinking skills, while “activities that promote physical activity would be helpful with respect to cardiovascular health, but no studies have really explored this.”
Researchers at the University of California at Davis compared changes in birth outcomes for mothers who likely received the largest increases in their EITCs under the expansions of the 1990s and mothers who likely received the smallest increases.  They found that infants born to mothers who likely received the largest increases had the greatest improvements in a number of birth indicators, such as fewer low-weight births and premature births.  Also, mothers who likely received the largest increases were likelier to receive prenatal care, including care before the critical third trimester, and to smoke and drink less during pregnancy. Changes in health insurance coverage did not seem to be a primary explanation for these improved health outcomes. 
The usual economic analysis of externalities can be illustrated using a standard supply and demand diagram if the externality can be valued in terms of money . An extra supply or demand curve is added, as in the diagrams below. One of the curves is the private cost that consumers pay as individuals for additional quantities of the good, which in competitive markets, is the marginal private cost. The other curve is the true cost that society as a whole pays for production and consumption of increased production the good, or the marginal social cost . Similarly there might be two curves for the demand or benefit of the good. The social demand curve would reflect the benefit to society as a whole, while the normal demand curve reflects the benefit to consumers as individuals and is reflected as effective demand in the market.