RFNBX vs. VIIIX

Last updated Jun 4, 2026

RFNBX (American Funds Fundamental Investors Fund Class R2) and VIIIX (Vanguard Institutional Index Fund Institutional Plus Shares) are both mutual funds - RFNBX is a Large Cap Blend Equities fund actively managed by Capital Group, while VIIIX is a S&P 500 fund tracking the S&P 500 Index. RFNBX is actively managed, while VIIIX is passively managed. Over the past 10 years, RFNBX returned 13.85%/yr vs 15.74%/yr for VIIIX. With a 0.96 correlation, they move nearly in lockstep. RFNBX charges 1.36%/yr vs 0.02%/yr for VIIIX.

Performance

RFNBX vs. VIIIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American Funds Fundamental Investors Fund Class R2 (RFNBX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, RFNBX achieves a 14.77% return, which is significantly higher than VIIIX's 11.70% return. Over the past 10 years, RFNBX has underperformed VIIIX with an annualized return of 13.85%, while VIIIX has yielded a comparatively higher 15.74% annualized return.

RFNBX

• 1D: 0.01%
• 1M: 5.83%
• YTD: 14.77%
• 6M: 15.70%
• 1Y: 33.49%
• 3Y*: 25.11%
• 5Y*: 14.02%
• 10Y*: 13.85%

VIIIX

• 1D: 0.13%
• 1M: 5.80%
• YTD: 11.70%
• 6M: 11.74%
• 1Y: 28.99%
• 3Y*: 23.17%
• 5Y*: 14.42%
• 10Y*: 15.74%

*Multi-year figures are annualized to reflect compound growth (CAGR)

RFNBX vs. VIIIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
RFNBX American Funds Fundamental Investors Fund Class R2	14.77%	23.22%	21.80%	24.89%	-17.32%	21.49%	12.51%	26.09%	-8.89%	21.82%
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	11.70%	17.87%	26.29%	25.79%	-18.14%	28.69%	18.41%	31.48%	-4.41%	21.82%

Correlation

The correlation between RFNBX and VIIIX is 0.93, indicating a strong positive relationship between their price movements. Combining them offers limited diversification - they tend to fall together during downturns.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.93
Correlation (3Y) Calculated over the trailing 3-year period	0.95
Correlation (5Y) Calculated over the trailing 5-year period	0.96
Correlation (10Y) Calculated over the trailing 10-year period	0.96
Correlation (All Time) Calculated using the full available price history since Jan 3, 2003	0.96

The correlation between RFNBX and VIIIX has been stable across timeframes, ranging from 0.93 to 0.96 - a consistent structural relationship.

Return for Risk

RFNBX vs. VIIIX — Risk / Return Rank

Compare risk-adjusted metric ranks to identify better-performing investments over the past 12 months.

RFNBX

RFNBX Risk / Return Rank: 70
RFNBX Sharpe Ratio Rank: 74
RFNBX Sortino Ratio Rank: 65
RFNBX Omega Ratio Rank: 65
RFNBX Calmar Ratio Rank: 68
RFNBX Martin Ratio Rank: 78

VIIIX

VIIIX Risk / Return Rank: 73
VIIIX Sharpe Ratio Rank: 76
VIIIX Sortino Ratio Rank: 67
VIIIX Omega Ratio Rank: 67
VIIIX Calmar Ratio Rank: 74
VIIIX Martin Ratio Rank: 83

The rank (0–100) shows how this investment's returns compare to the risk taken. Higher = better. Based on the past 12 months of data, combining Sharpe, Sortino, and other metrics used by quantitative funds and institutional investors.

RFNBX vs. VIIIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Funds Fundamental Investors Fund Class R2 (RFNBX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX). Risk-adjusted metrics are performance indicators that assess an investment's returns in relation to its risk, enabling a more accurate comparison of different investment options.

	RFNBX	VIIIX	Difference
Sharpe ratio: Return per unit of total volatility	2.51	2.52	-0.01
Sortino ratio: Return per unit of downside risk	3.37	3.42	-0.06
Omega ratio: Gain probability vs. loss probability	1.45	1.46	-0.01
Calmar ratio: Return relative to maximum drawdown	3.20	3.36	-0.16
Martin ratio: Return relative to average drawdown	14.72	15.69	-0.97
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

RFNBX vs. VIIIX - Sharpe Ratio Comparison

The current RFNBX Sharpe Ratio is 2.51, which is comparable to the VIIIX Sharpe Ratio of 2.52. The chart below compares the historical Sharpe Ratios of RFNBX and VIIIX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Sharpe Ratios by Period

	RFNBX	VIIIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.51	2.52	-0.01
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.84	0.86	-0.02
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.78	0.87	-0.09
Sharpe Ratio (All Time) Calculated using the full available price history	0.60	0.50	+0.11

Drawdowns

RFNBX vs. VIIIX - Drawdown Comparison

The maximum RFNBX drawdown since its inception was -53.81%, roughly equal to the maximum VIIIX drawdown of -55.18%. Use the drawdown chart below to compare losses from any high point for RFNBX and VIIIX.

Drawdown Indicators

	RFNBX	VIIIX	Difference
Max Drawdown Largest peak-to-trough decline	-53.81%	-55.18%	+1.37%
Max Drawdown (1Y) Largest decline over 1 year	-10.78%	-8.90%	-1.88%
Max Drawdown (3Y) Largest decline over 3 years	-18.11%	-18.75%	+0.64%
Max Drawdown (5Y) Largest decline over 5 years	-25.53%	-24.50%	-1.03%
Max Drawdown (10Y) Largest decline over 10 years	-33.96%	-33.79%	-0.17%
Current Drawdown Current decline from peak	0.00%	0.00%	0.00%
Average Drawdown Average peak-to-trough decline	-7.24%	-10.02%	+2.78%
Ulcer Index Depth and duration of drawdowns from previous peaks	2.33%	1.90%	+0.43%

Volatility

RFNBX vs. VIIIX - Volatility Comparison

American Funds Fundamental Investors Fund Class R2 (RFNBX) has a higher volatility of 3.69% compared to Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX) at 2.83%. This indicates that RFNBX's price experiences larger fluctuations and is considered to be riskier than VIIIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	RFNBX	VIIIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	3.69%	2.83%	+0.86%
Volatility (6M) Calculated over the trailing 6-month period	10.82%	8.97%	+1.85%
Volatility (1Y) Calculated over the trailing 1-year period	13.75%	11.86%	+1.89%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	16.80%	16.89%	-0.09%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	17.74%	18.06%	-0.32%

RFNBX vs. VIIIX - Expense Ratio Comparison

RFNBX has a 1.36% expense ratio, which is higher than VIIIX's 0.02% expense ratio.

Dividends

RFNBX vs. VIIIX - Dividend Comparison

RFNBX's dividend yield for the trailing twelve months is around 6.87%, more than VIIIX's 2.41% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
RFNBX American Funds Fundamental Investors Fund Class R2	6.87%	7.90%	8.19%	5.13%	4.16%	10.27%	0.83%	6.20%	8.38%	6.54%	3.99%	5.32%
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	2.41%	2.11%	3.66%	2.66%	3.39%	4.79%	3.07%	2.86%	2.45%	1.84%	2.38%	2.47%

Frequently Asked Questions

Can I hold both RFNBX and VIIIX in my portfolio?

With a correlation of 0.93, RFNBX and VIIIX move almost identically. Holding both adds very little diversification - you're essentially doubling your position in the same market segment. Choosing one is usually more capital-efficient.

Which is riskier, RFNBX or VIIIX?

RFNBX has higher volatility (3.69%) compared to VIIIX (2.83%). In terms of maximum drawdown, RFNBX dropped -53.81% vs VIIIX's -55.18%.

Which has better risk-adjusted returns?

VIIIX currently has the higher Sharpe Ratio (2.52 vs 2.51), meaning it's delivered slightly more return per unit of risk over the trailing 12 months. However, this ranking shifts over time - use the Risk/Return Score above for a more comprehensive view that combines Sharpe, Sortino, and other measures used by quantitative funds.