VFFSX vs. RCKSX

Last updated Jun 4, 2026

VFFSX (Vanguard 500 Index Fund Institutional Select Shares) and RCKSX (Rock Oak Core Growth Fund) are both Large Cap Blend Equities funds. Over the past 5 years, VFFSX returned 14.27%/yr vs 7.42%/yr for RCKSX. Their correlation of 0.84 suggests significant overlap in exposure. VFFSX charges 0.01%/yr vs 1.25%/yr for RCKSX.

Performance

VFFSX vs. RCKSX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Vanguard 500 Index Fund Institutional Select Shares (VFFSX) and Rock Oak Core Growth Fund (RCKSX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, VFFSX achieves a 11.71% return, which is significantly lower than RCKSX's 14.10% return.

VFFSX

• 1D: 0.13%
• 1M: 5.80%
• YTD: 11.71%
• 6M: 11.74%
• 1Y: 28.99%
• 3Y*: 22.76%
• 5Y*: 14.27%
• 10Y*: —

RCKSX

• 1D: -0.13%
• 1M: 1.87%
• YTD: 14.10%
• 6M: 14.42%
• 1Y: 20.18%
• 3Y*: 19.62%
• 5Y*: 7.42%
• 10Y*: 10.85%

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

VFFSX vs. RCKSX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
VFFSX Vanguard 500 Index Fund Institutional Select Shares	11.71%	17.87%	25.00%	26.28%	-18.14%	29.24%	18.35%	31.88%	-4.42%	20.80%
RCKSX Rock Oak Core Growth Fund	14.10%	12.99%	15.12%	15.57%	-18.09%	9.96%	13.75%	19.05%	-2.14%	21.60%

Correlation

The correlation between VFFSX and RCKSX is 0.63, which is moderate. They share some common price drivers but move independently often enough to provide real diversification benefit when combined.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.63
Correlation (3Y) Calculated over the trailing 3-year period	0.72
Correlation (5Y) Calculated over the trailing 5-year period	0.81
Correlation (All Time) Calculated using the full available price history since Jan 4, 2017	0.84

Over the past year, the correlation between VFFSX and RCKSX has dropped to 0.63 - well below their long-term average of 0.84, suggesting their price drivers have been diverging.

Return for Risk

VFFSX vs. RCKSX — Risk / Return Rank

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

VFFSX

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

RCKSX

RCKSX Risk / Return Rank: 56
RCKSX Sharpe Ratio Rank: 39
RCKSX Sortino Ratio Rank: 40
RCKSX Omega Ratio Rank: 34
RCKSX Calmar Ratio Rank: 93
RCKSX Martin Ratio Rank: 75

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.

VFFSX vs. RCKSX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Vanguard 500 Index Fund Institutional Select Shares (VFFSX) and Rock Oak Core Growth Fund (RCKSX). 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.

	VFFSX	RCKSX	Difference
Sharpe ratio: Return per unit of total volatility	2.52	1.83	+0.69
Sortino ratio: Return per unit of downside risk	3.42	2.66	+0.77
Omega ratio: Gain probability vs. loss probability	1.46	1.31	+0.15
Calmar ratio: Return relative to maximum drawdown	3.36	5.11	-1.75
Martin ratio: Return relative to average drawdown	15.70	14.18	+1.51
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

VFFSX vs. RCKSX - Sharpe Ratio Comparison

The current VFFSX Sharpe Ratio is 2.52, which is higher than the RCKSX Sharpe Ratio of 1.83. The chart below compares the historical Sharpe Ratios of VFFSX and RCKSX, 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

	VFFSX	RCKSX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.52	1.83	+0.69
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.85	0.48	+0.37
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	—	0.62	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.86	0.38	+0.48

Drawdowns

VFFSX vs. RCKSX - Drawdown Comparison

The maximum VFFSX drawdown since its inception was -33.82%, smaller than the maximum RCKSX drawdown of -57.88%. Use the drawdown chart below to compare losses from any high point for VFFSX and RCKSX.

Drawdown Indicators

	VFFSX	RCKSX	Difference
Max Drawdown Largest peak-to-trough decline	-33.82%	-57.88%	+24.06%
Max Drawdown (1Y) Largest decline over 1 year	-8.90%	-4.14%	-4.76%
Max Drawdown (3Y) Largest decline over 3 years	-18.75%	-18.22%	-0.53%
Max Drawdown (5Y) Largest decline over 5 years	-24.51%	-22.54%	-1.97%
Max Drawdown (10Y) Largest decline over 10 years	—	-33.10%	—
Current Drawdown Current decline from peak	0.00%	-0.60%	+0.60%
Average Drawdown Average peak-to-trough decline	-4.50%	-9.51%	+5.01%
Ulcer Index Depth and duration of drawdowns from previous peaks	1.90%	1.49%	+0.41%

Volatility

VFFSX vs. RCKSX - Volatility Comparison

Vanguard 500 Index Fund Institutional Select Shares (VFFSX) and Rock Oak Core Growth Fund (RCKSX) have volatilities of 2.83% and 2.94%, respectively, indicating that both stocks experience similar levels of price fluctuations. This suggests that the risk associated with both stocks, as measured by volatility, is nearly the same. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	VFFSX	RCKSX	Difference
Volatility (1M) Calculated over the trailing 1-month period	2.83%	2.94%	-0.11%
Volatility (6M) Calculated over the trailing 6-month period	8.98%	8.06%	+0.92%
Volatility (1Y) Calculated over the trailing 1-year period	11.86%	11.56%	+0.30%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	16.90%	15.66%	+1.24%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.41%	17.55%	+0.86%

VFFSX vs. RCKSX - Expense Ratio Comparison

VFFSX has a 0.01% expense ratio, which is lower than RCKSX's 1.25% expense ratio.

Dividends

VFFSX vs. RCKSX - Dividend Comparison

VFFSX's dividend yield for the trailing twelve months is around 1.03%, less than RCKSX's 5.48% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
RCKSX Rock Oak Core Growth Fund	5.48%	6.26%	0.47%	0.71%	1.00%	4.31%	16.56%	3.18%	0.59%	5.91%	0.70%	3.21%
VFFSX Vanguard 500 Index Fund Institutional Select Shares	1.03%	1.14%	1.24%	1.46%	1.70%	1.61%	1.56%	2.15%	2.09%	1.81%	0.00%	0.00%

Frequently Asked Questions

Can I hold both VFFSX and RCKSX in my portfolio?

VFFSX and RCKSX have a correlation of 0.63, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, VFFSX or RCKSX?

RCKSX has higher volatility (2.94%) compared to VFFSX (2.83%). In terms of maximum drawdown, VFFSX dropped -33.82% vs RCKSX's -57.88%.

Which has better risk-adjusted returns?

VFFSX currently has the higher Sharpe Ratio (2.52 vs 1.83), 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.