NOSIX vs. PRBLX

Last updated Jun 23, 2026

NOSIX (Northern Stock Index Fund) and PRBLX (Parnassus Core Equity Fund) are both Large Cap Blend Equities funds. Over the past 10 years, NOSIX returned 15.48%/yr vs 13.76%/yr for PRBLX. Their correlation of 0.89 suggests significant overlap in exposure. NOSIX charges 0.05%/yr vs 0.82%/yr for PRBLX.

Performance

NOSIX vs. PRBLX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Northern Stock Index Fund (NOSIX) and Parnassus Core Equity Fund (PRBLX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, NOSIX achieves a 10.17% return, which is significantly higher than PRBLX's 7.77% return. Over the past 10 years, NOSIX has outperformed PRBLX with an annualized return of 15.48%, while PRBLX has yielded a comparatively lower 13.76% annualized return.

NOSIX

• 1D: 1.08%
• 1M: 0.47%
• YTD: 10.17%
• 6M: 9.68%
• 1Y: 26.89%
• 3Y*: 20.93%
• 5Y*: 14.01%
• 10Y*: 15.48%

PRBLX

• 1D: 1.65%
• 1M: 2.48%
• YTD: 7.77%
• 6M: 7.55%
• 1Y: 16.44%
• 3Y*: 15.69%
• 5Y*: 10.64%
• 10Y*: 13.76%

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

NOSIX vs. PRBLX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
NOSIX Northern Stock Index Fund	10.17%	17.83%	24.87%	26.24%	-18.25%	28.55%	18.33%	31.35%	-4.54%	21.71%
PRBLX Parnassus Core Equity Fund	7.77%	11.67%	18.58%	24.97%	-18.64%	27.59%	21.21%	30.68%	-0.30%	16.63%

Correlation

The correlation between NOSIX and PRBLX is 0.79, 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	0.79
Correlation (3Y) Calculated over the trailing 3-year period	0.89
Correlation (5Y) Calculated over the trailing 5-year period	0.93
Correlation (10Y) Calculated over the trailing 10-year period	0.93
Correlation (All Time) Calculated using the full available price history since Oct 7, 1996	0.89

The correlation between NOSIX and PRBLX shifts across timeframes, from 0.79 (1 year) to 0.93 (10 years), reflecting how their relationship changes across market environments.

Return for Risk

NOSIX vs. PRBLX — Risk / Return Rank

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

NOSIX

NOSIX Risk / Return Rank: 67
NOSIX Sharpe Ratio Rank: 65
NOSIX Sortino Ratio Rank: 60
NOSIX Omega Ratio Rank: 63
NOSIX Calmar Ratio Rank: 69
NOSIX Martin Ratio Rank: 80

PRBLX

PRBLX Risk / Return Rank: 22
PRBLX Sharpe Ratio Rank: 24
PRBLX Sortino Ratio Rank: 23
PRBLX Omega Ratio Rank: 22
PRBLX Calmar Ratio Rank: 17
PRBLX Martin Ratio Rank: 24

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.

NOSIX vs. PRBLX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Northern Stock Index Fund (NOSIX) and Parnassus Core Equity Fund (PRBLX). 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.

Values are calculated on a 1-year rolling basis and updated daily. Risk-adjusted metrics are more stable over longer periods — use the period switch above to explore them.

	NOSIX	PRBLX	Difference
Sharpe ratio: Return per unit of total volatility	2.17	1.31	+0.86
Sortino ratio: Return per unit of downside risk	2.96	1.87	+1.10
Omega ratio: Gain probability vs. loss probability	1.40	1.23	+0.17
Calmar ratio: Return relative to maximum drawdown	3.07	1.39	+1.68
Martin ratio: Return relative to average drawdown	13.88	5.38	+8.50

NOSIX vs. PRBLX - Sharpe Ratio Comparison

The current NOSIX Sharpe Ratio is 2.17, which is higher than the PRBLX Sharpe Ratio of 1.31. The chart below compares the historical Sharpe Ratios of NOSIX and PRBLX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Drawdowns

NOSIX vs. PRBLX - Drawdown Comparison

The maximum NOSIX drawdown since its inception was -55.42%, which is greater than PRBLX's maximum drawdown of -42.20%. Use the drawdown chart below to compare losses from any high point for NOSIX and PRBLX.

Drawdown Indicators

	NOSIX	PRBLX	Difference
Max Drawdown Largest peak-to-trough decline	-55.42%	-42.20%	-13.22%
Max Drawdown (1Y) Largest decline over 1 year	-8.89%	-11.63%	+2.74%
Max Drawdown (3Y) Largest decline over 3 years	-18.75%	-16.31%	-2.44%
Max Drawdown (5Y) Largest decline over 5 years	-24.54%	-26.31%	+1.77%
Max Drawdown (10Y) Largest decline over 10 years	-33.82%	-30.09%	-3.73%
Current Drawdown Current decline from peak	-1.34%	-0.13%	-1.21%
Average Drawdown Average peak-to-trough decline	-10.32%	-4.04%	-6.28%
Ulcer Index Depth and duration of drawdowns from previous peaks	1.95%	2.98%	-1.03%

Volatility

NOSIX vs. PRBLX - Volatility Comparison

Northern Stock Index Fund (NOSIX) and Parnassus Core Equity Fund (PRBLX) have volatilities of 4.75% and 4.67%, 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

	NOSIX	PRBLX	Difference
Volatility (1M) Calculated over the trailing 1-month period	4.75%	4.67%	+0.08%
Volatility (6M) Calculated over the trailing 6-month period	9.90%	9.97%	-0.07%
Volatility (1Y) Calculated over the trailing 1-year period	12.56%	12.35%	+0.21%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	17.29%	16.34%	+0.95%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.25%	17.31%	+0.94%

NOSIX vs. PRBLX - Expense Ratio Comparison

NOSIX has a 0.05% expense ratio, which is lower than PRBLX's 0.82% expense ratio.

Dividends

NOSIX vs. PRBLX - Dividend Comparison

NOSIX's dividend yield for the trailing twelve months is around 2.67%, less than PRBLX's 17.66% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
NOSIX Northern Stock Index Fund	2.67%	2.94%	2.59%	5.02%	4.72%	3.22%	4.00%	2.41%	4.82%	3.13%	2.76%	3.36%
PRBLX Parnassus Core Equity Fund	17.66%	19.08%	10.00%	6.01%	10.13%	7.77%	5.87%	8.02%	9.64%	7.16%	3.80%	9.62%

Frequently Asked Questions

Can I hold both NOSIX and PRBLX in my portfolio?

NOSIX and PRBLX have a correlation of 0.79, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, NOSIX or PRBLX?

NOSIX has higher volatility (4.75%) compared to PRBLX (4.67%). In terms of maximum drawdown, NOSIX dropped -55.42% vs PRBLX's -42.20%.

Which has better risk-adjusted returns?

NOSIX currently has the higher Sharpe Ratio (2.17 vs 1.31), 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.