Index 600 Stock Portfolio
Data updated: 2026-08-20
C000050279 — Index 600 Stock Portfolio. United States Small Cap Blend / Core Equity · $618.98M AUM. Holdings, fees, performance and SEC filings.
C000050279 Fund Overview
Index 600 Stock Portfolio is a US mutual fund managed by Northwestern Mutual Series Fund INC, categorised as United States Small Cap Blend / Core Equity. ABC INVEST provides holdings, performance, costs, cashflows, risk data, prospectus documents and SEC filings, sourced from SEC filings.
- Type: US mutual fund
- Manager: Northwestern Mutual Series Fund INC
- Category: United States Small Cap Blend / Core Equity
- Assets under management: $618.98M
- 1-year return: 37.2%
- SEC CIK: 0000742212
- SEC series ID: S000018231
- Share class ID: C000050279
C000050279 Investment Objective and Strategy
Index 600 Stock Portfolio describes its objective and strategy as follows, from its latest prospectus filed with the SEC by Northwestern Mutual Series Fund INC.
Investment objective
The investment objective of the Portfolio is to achieve investment results that approximate the performance of the Standard & Poors SmallCap 600 Index (S&P SmallCap 600 Index).
Principal investment strategy
The Portfolio employs a passive management, or indexing, investment approach designed to track the performance of the S&P SmallCap 600 Index. S&P SmallCap 600 Index is composed of domestic stocks with market capitalizations ranging between approximately $ 442.41 million and $8.78 billion as of March 31, 2026. Normally, the Portfolio invests at least 80% of net assets (plus any borrowings for investment purposes) in stocks included in the underlying index. Further, the Portfolio attempts to achieve its objective by investing all, or substantially all, of its assets in stocks that make up the S&P SmallCap 600 Index, holding each stock in approximately the same proportion as its weighting in the Index. This is known as a full replication strategy. The Portfolio may also invest in equity index futures and exchange traded funds for cash management and liquidity purposes and to help achieve full replication.
Standard & Poors constructs the index by first identifying major industry categories and then allocating a representative sample of the larger and more liquid stocks in those industries to the index. S&P weights each stock according to its float-adjusted market value. For example, the 50 largest companies in the index may account for over 50% of its value. The approach employed by the Portfolio with respect to reconstitution and rebalancing aligns with the process followed generally by the S&P SmallCap 600 Index. Changes to the underlying company constituents of the S&P SmallCap 600 Index are made on an as-needed basis and are usually announced several days before they are scheduled to be implemented. The S&P SmallCap 600 Index typically makes weightings adjustments based on changes in the amount of a constituent companys shares outstanding on a quarterly basis.
The constituent and share-based weightings changes made by S&P SmallCap 600 Index will be made in a parallel fashion by the Portfolio on substantially the same timeline. Because the Portfolio pursues an investment strategy of full replication of the underlying S&P SmallCap 600 Index, investments in the Portfolio will be concentrated in a particular industry only to the extent that the S&P SmallCap 600 Index is also concentrated in that industry. Similarly, to the extent that the underlying S&P SmallCap 600 Index has a relatively high percentage of its assets invested in a particular sector, the Portfolio may also hold a relatively high percentage of its assets in that particular sector, as well. The Portfolio utilizes cash equitization instruments, and rebalancing occurs as necessary to maintain balances within established target ranges for these instruments.
Cash equitization as employed by the Portfolio is a strategy pursuant to which the Portfolio will acquire certain derivative instruments, such as equity index futures, whereby the futures will be utilized to replicate index returns and enable the Portfolio to be fully invested, while still maintaining cash balances as needed by the Portfolio. This strategy works to limit the extent to which uninvested cash will weigh negatively on overall Portfolio returns when markets go up. The Index 600 Stock Portfolios ability to match the performance of the S&P SmallCap 600 Index will be affected to some extent by the size and timing of cash flows into and out of the Index 600 Stock Portfolio. The Portfolio will be managed with a view to reducing such effects.
C000050279 Holdings
Top 10 holdings of Index 600 Stock Portfolio by percentage of net assets, from the fund's latest SEC N-PORT filing.
| Holding | % of net assets |
|---|---|
| FormFactor Inc | 0.67% |
| Viasat Inc | 0.66% |
| Molina Healthcare Inc | 0.64% |
| Argan Inc | 0.60% |
| BrightSpring Health Services Inc | 0.60% |
| Element Solutions Inc | 0.59% |
| MaxLinear Inc | 0.58% |
| Krystal Biotech Inc | 0.53% |
| ESCO Technologies Inc | 0.49% |
| Match Group Inc | 0.48% |
C000050279 Portfolio Allocation
Asset-class allocation of Index 600 Stock Portfolio by percentage of net assets, from the latest SEC N-PORT filing.
| Asset class | Allocation |
|---|---|
| Equity | 99.4% |
C000050279 Performance
Total returns for C000050279 (as of 2026-10-01), from SEC filings.
| Period | Total return |
|---|---|
| YTD | 23.7% |
| 1 year | 37.2% |
| 3 years (annualised) | 15.8% |
| 5 years (annualised) | 7.1% |
C000050279 Risk Information
Risk metrics for C000050279, derived from monthly returns in SEC filings.
- 1-year volatility (annualised): 14.1%
C000050279 Costs and Fees
C000050279 costs about $26 per $10,000 invested per year in fund expenses.
- Net expense ratio: 0.26%
- Gross expense ratio: 0.26%
- Portfolio turnover: 24%
- Brokerage commissions: 0.21 bps of average net assets (SEC N-CEN)
C000050279 Cashflows
Over the 12 months to 2026-06, Index 600 Stock Portfolio had net inflows of $6.56M, from monthly SEC N-PORT filings.
| Month | Net flow |
|---|---|
| 2026-06 | −$3.69M |
| 2026-05 | −$3.59M |
| 2026-04 | −$2.09M |
| 2026-03 | −$2.41M |
| 2026-02 | −$4.00M |
| 2026-01 | −$86.85K |
C000050279 Debt Constituents
No individual debt constituents are reported in Index 600 Stock Portfolio's latest SEC N-PORT filing.
C000050279 Prospectus and SEC Filings
Official Index 600 Stock Portfolio filings on SEC EDGAR — prospectus, portfolio holdings and annual reports.
- Prospectus (485BPOS) — filed 2026-04-24
- Prospectus (485BPOS) — filed 2025-04-25
- Prospectus supplement (497) — filed 2024-04-30
- Portfolio holdings (N-PORT) — filed 2026-08-20
- Portfolio holdings (N-PORT) — filed 2026-05-27
- Portfolio holdings (N-PORT) — filed 2026-02-23
- Annual census (N-CEN) — filed 2026-03-12
- Annual census (N-CEN) — filed 2025-03-11
Related Funds
Other United States Small Cap Blend / Core Equity funds tracked on ABC INVEST:
Data Sources
ABC INVEST compiles this page from public filings made to the U.S. Securities and Exchange Commission (SEC) through EDGAR: portfolio holdings and monthly cashflows from Form N-PORT, expenses and returns from fund prospectuses (Form 485BPOS) and the SEC DERA Risk/Return Summary data sets, annual data from Form N-CEN, and shareholder reports from Form N-CSR.