An investor holds a portfolio of 30 stocks, all in the oil and gas sector. They believe this is well diversified because it contains many individual positions. What is the main flaw in this reasoning?
AHolding 30 stocks is too many — optimal diversification is achieved with exactly 10 to 15 stocks regardless of sector
BThe portfolio is actually well diversified because academic research shows that any 30 randomly selected stocks eliminate virtually all risk, sector concentration included
CDiversification requires exposure across sectors and asset classes, not just a large number of holdings — stocks in the same sector tend to be driven by the same risk factors (oil prices, regulation, geopolitical supply shocks), so a 30-stock single-sector portfolio still carries concentrated sector risk
DDiversification only matters for bond portfolios; equity portfolios benefit from concentration because it allows the investor to develop deep sector expertise
According to Modern Portfolio Theory, what does the 'efficient frontier' represent?
AThe line connecting the risk-free rate to the highest-returning asset in the investable universe, representing the only rational investment strategy
BThe set of portfolios that offer the highest expected return for each level of risk (standard deviation), meaning no portfolio on the frontier can increase its expected return without also increasing its risk
CA single optimal portfolio that every investor should hold, regardless of their individual risk preferences or investment horizon
DThe boundary below which all portfolios are considered too risky for any rational investor, regardless of their risk tolerance
Two assets have expected returns of 8% and 12% respectively. If their returns are perfectly negatively correlated (correlation coefficient of −1), what is theoretically possible when combining them in a portfolio?
ANegative correlation has no effect on portfolio risk; only the individual standard deviations of each asset determine the portfolio's total risk regardless of how the assets co-move
BThe portfolio's expected return can exceed 12%, because negative correlation creates a synergy bonus that amplifies returns beyond either individual asset
CA correlation of −1 means one asset always gains exactly what the other loses, so combining them always produces a return of zero — the assets cancel each other out entirely
DThe portfolio's risk (standard deviation) can be reduced to zero at a specific weighting, while the expected return falls between 8% and 12% depending on the allocation chosen