TSTFX vs. VIIIX

Last updated Jun 4, 2026

TSTFX (Transamerica Stock Index) and VIIIX (Vanguard Institutional Index Fund Institutional Plus Shares) are both mutual funds - TSTFX is a Large Cap Blend Equities fund managed by Transamerica, while VIIIX is a S&P 500 fund tracking the S&P 500 Index. Over the past 5 years, TSTFX returned 6.41%/yr vs 14.42%/yr for VIIIX. With a 0.96 correlation, they move nearly in lockstep. TSTFX charges 0.30%/yr vs 0.02%/yr for VIIIX.

Performance

TSTFX vs. VIIIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Transamerica Stock Index (TSTFX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

The year-to-date returns for both investments are quite close, with TSTFX having a 11.55% return and VIIIX slightly higher at 11.70%.

TSTFX

• 1D: 0.11%
• 1M: 5.79%
• YTD: 11.55%
• 6M: -21.00%
• 1Y: -8.95%
• 3Y*: 9.00%
• 5Y*: 6.41%
• 10Y*: —

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)

TSTFX vs. VIIIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
TSTFX Transamerica Stock Index	11.55%	-17.03%	24.66%	25.99%	-18.27%	28.84%	18.10%	31.17%	-4.75%	14.78%
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%	15.59%

Correlation

The correlation between TSTFX and VIIIX is 0.84, 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	0.84
Correlation (3Y) Calculated over the trailing 3-year period	0.87
Correlation (5Y) Calculated over the trailing 5-year period	0.93
Correlation (All Time) Calculated using the full available price history since Mar 23, 2017	0.96

The correlation between TSTFX and VIIIX shifts across timeframes, from 0.84 (1 year) to 0.96 (all time), reflecting how their relationship changes across market environments.

Return for Risk

TSTFX vs. VIIIX — Risk / Return Rank

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

TSTFX

TSTFX Risk / Return Rank: 2
TSTFX Sharpe Ratio Rank: 2
TSTFX Sortino Ratio Rank: 2
TSTFX Omega Ratio Rank: 2
TSTFX Calmar Ratio Rank: 2
TSTFX Martin Ratio Rank: 2

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.

TSTFX vs. VIIIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Transamerica Stock Index (TSTFX) 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.

	TSTFX	VIIIX	Difference
Sharpe ratio: Return per unit of total volatility	-0.29	2.52	-2.81
Sortino ratio: Return per unit of downside risk	-0.12	3.42	-3.54
Omega ratio: Gain probability vs. loss probability	0.96	1.46	-0.50
Calmar ratio: Return relative to maximum drawdown	-0.27	3.36	-3.63
Martin ratio: Return relative to average drawdown	-0.47	15.69	-16.16
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

TSTFX vs. VIIIX - Sharpe Ratio Comparison

The current TSTFX Sharpe Ratio is -0.29, which is lower than the VIIIX Sharpe Ratio of 2.52. The chart below compares the historical Sharpe Ratios of TSTFX 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

	TSTFX	VIIIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	-0.29	2.52	-2.81
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.31	0.86	-0.55
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	—	0.87	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.53	0.50	+0.04

Drawdowns

TSTFX vs. VIIIX - Drawdown Comparison

The maximum TSTFX drawdown since its inception was -34.74%, smaller than the maximum VIIIX drawdown of -55.18%. Use the drawdown chart below to compare losses from any high point for TSTFX and VIIIX.

Drawdown Indicators

	TSTFX	VIIIX	Difference
Max Drawdown Largest peak-to-trough decline	-34.74%	-55.18%	+20.44%
Max Drawdown (1Y) Largest decline over 1 year	-34.74%	-8.90%	-25.84%
Max Drawdown (3Y) Largest decline over 3 years	-34.74%	-18.75%	-15.99%
Max Drawdown (5Y) Largest decline over 5 years	-34.74%	-24.50%	-10.24%
Max Drawdown (10Y) Largest decline over 10 years	—	-33.79%	—
Current Drawdown Current decline from peak	-21.59%	0.00%	-21.59%
Average Drawdown Average peak-to-trough decline	-6.04%	-10.02%	+3.98%
Ulcer Index Depth and duration of drawdowns from previous peaks	18.90%	1.90%	+17.00%

Volatility

TSTFX vs. VIIIX - Volatility Comparison

Transamerica Stock Index (TSTFX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX) have volatilities of 2.81% and 2.83%, 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

	TSTFX	VIIIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	2.81%	2.83%	-0.02%
Volatility (6M) Calculated over the trailing 6-month period	34.38%	8.97%	+25.41%
Volatility (1Y) Calculated over the trailing 1-year period	32.29%	11.86%	+20.43%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	21.51%	16.89%	+4.62%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	21.01%	18.06%	+2.95%

TSTFX vs. VIIIX - Expense Ratio Comparison

TSTFX has a 0.30% expense ratio, which is higher than VIIIX's 0.02% expense ratio.

Dividends

TSTFX vs. VIIIX - Dividend Comparison

TSTFX's dividend yield for the trailing twelve months is around 0.87%, less than VIIIX's 2.41% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
TSTFX Transamerica Stock Index	0.87%	0.70%	2.61%	4.32%	6.77%	6.57%	4.69%	5.60%	4.69%	2.85%	0.00%	0.00%
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 TSTFX and VIIIX in my portfolio?

TSTFX and VIIIX have a correlation of 0.84, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, TSTFX or VIIIX?

VIIIX has higher volatility (2.83%) compared to TSTFX (2.81%). In terms of maximum drawdown, TSTFX dropped -34.74% vs VIIIX's -55.18%.

Which has better risk-adjusted returns?

VIIIX currently has the higher Sharpe Ratio (2.52 vs -0.29), 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.