Families that own stocks: The percentage of American households that own publicly traded s...

Families that own stocks: The percentage of American households that own publicly traded stocks began rising in the early 1950s, peaked in 1970, then began to decline until 1980 when there was a dramatic increase due to easy access over the Internet, an improved economy, and other factors. This phenomenon is modeled by the function P(t), where P(t) represents the percentage of households owning stock in year t, with 1950 corresponding to year 0.

a. According to this model, what percentage of American households held stock in the years 1955, 1965, 1975, 1985, and 1995? If this pattern continues, what percentage held stock in 2005? What percent will hold stock in 2015?

b. Why is there a discrepancy in the outputs of each piece of the function for the year 1980 (t = 30)? According to how the function is defined, which output should be used?

Source: 2004 Statistical Abstract of the United States, Table 1204; various other years.