FYI: The next time somebody propounds the notion of efficient markets, do smile politely.
You may reasonably concede that all possible knowledge about the 500 biggest stocks is fully discounted in their prices, so passive ownership of that broad index beats active stock picking. But when it comes to bonds and bond funds, the exceptions are prevalent enough to dispute the efficient-market rule.
This is by way of introduction to two such examples. First, consider the T. Rowe Price High Yield fund (ticker: PRHYX), which has consistently out-returned the popular exchange-traded index fund that tracks the junk market, the iShares iBoxx $ High Yield Corporate Bond ETF (HYG), over almost every time period.
Now consider the New America High Income fund (HYB), which has consistently outperformed the T. Rowe Price open-end fund even though both share the same managers and much the same portfolio. The key difference between the two is the former is a closed-end fund, which means it has a fixed number of shares, while the latter is an open-end mutual fund, which means it expands and contracts the number of shares to accommodate investor purchases and redemptions.
M* Snapshot PRHYX:https://www.morningstar.com/funds/xnas/prhyx/quote.html
M* Snapshot HYB:https://www.morningstar.com/cefs/xnys/hyb/quote.html