Why did the proportion of equities in long-term funds increase from 38.3 percent in 1990 to more

Question:

Why did the proportion of equities in long-term funds increase from 38.3 percent in 1990 to more than 70 percent by 2000, and then decrease to 54 percent in 2012? How might an investor’s preference for a objectives change over time?
Mutual Funds
Mutual funds are like a pool of funds gathered by different small investors that have simalar investment perspective about returns on their investments. These funds are managed by professional investment managers who act smartly on behalf of the...