The Stanford Research Institute (SRI), which analyzed the SIME/DIME findings, found stronger work disincentive effects, ranging from an average 9 percent work reduction for husbands to an average 18 percent reduction for wives. This was not as scary as some NIT opponents had predicted. But it was large enough to suggest that as much as 50 to 60 percent of the transfers paid to two-parent families under a NIT might go to replace lost earnings. They also found an unexpected result: instead of promoting family stability (the presumed result of extending benefits to two-parent working families on an equal basis), the NITs seemed to increase family breakup. 
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.