FlexShares Credit-Scored US Long Corporate Bond Index Fund (LKOR)

Corporate bonds—debt issued by large American companies—are among the most traded securities in the financial system. Investors buy them to earn a higher yield than Treasury bonds, but in exchange they accept the risk that the company might default. LKOR addresses that risk trade-off through a specific tool: proprietary credit scores. Rather than weighting bonds equally or by market cap, LKOR overweights the safest borrowers and underweights riskier ones, tilting the traditional investment-grade bond index toward quality.

What LKOR holds and why it exists

LKOR is an exchange-traded fund that invests in a diversified portfolio of US corporate bonds issued by large, investment-grade companies—debt maturing in roughly 10 years or longer (the “long” part of the fund’s name). The underlying universe is the Bloomberg US Corporate Bond Index, which includes thousands of bonds from companies across industrials, technology, finance, utilities, consumer goods, and other sectors.

But LKOR does not weight that universe equally or by market cap (as a traditional index fund would). Instead, it uses a proprietary credit-scoring system developed by the fund sponsor (Northern Trust/FlexShares) to assess the creditworthiness of each issuer. Bonds from companies with higher credit scores—companies that the model assesses as less likely to default—receive higher weights in the portfolio. Bonds from companies with lower credit scores receive lower weights. The result is a modified index that tilts toward the safest borrowers while maintaining diversification across issuers and sectors.

The credit-scoring methodology

Credit scoring in the corporate bond market is not new. Rating agencies like Moody’s and Standard & Poor’s have long assigned letter grades (AAA, AA, A, BBB, and below) to corporate bonds, signaling default risk. LKOR respects those ratings as one input but goes deeper. Its proprietary score incorporates:

• Traditional financial metrics: leverage ratios, interest-coverage ratios, debt maturity profiles, and cash flow metrics. These measure a company’s ability to service its debt from operating earnings.
• Market signals: the company’s stock price performance, implied volatility in options markets, and the credit-default swap spreads (which directly price the cost of insuring against default). When a company’s stock falls sharply or its credit default swap widens, the model recognizes that market participants are pricing in higher default risk.
• Fundamental business trends: revenue growth, profitability, competitive positioning, and management quality (where available from published sources).

The model synthesizes these inputs into a single credit score ranging (typically) from 0 to 100, with higher scores indicating lower perceived default risk. A company with a score of 80 might have a much lower default probability than a company with a score of 40, even if both are investment-grade (BBB- rated or above).

The result: a tilt toward quality without abandonment of diversification

LKOR’s weighting scheme is conservative. The fund does not exclude lower-scoring bonds (as long as they are investment-grade). Instead, it underweights them. This preserves diversification—the fund still holds bonds from hundreds of issuers—but concentrates more capital in the bonds FlexShares deems safest. Over a full market cycle, this tilts returns toward lower default risk.

In calm bond markets, where default risk is low, LKOR behaves much like any other investment-grade corporate bond fund—it captures the yield and earns returns similar to a broad index. But when credit stress rises and default risk increases, the credit-scoring tilt becomes valuable. Companies with high scores tend to outperform those with low scores; bonds from companies with deteriorating fundamentals fall in price while those from stronger companies hold up better. LKOR’s overweight to higher-scoring bonds acts as a shock absorber.

Yield and income

LKOR distributes the interest income it receives from its corporate bond holdings, typically monthly. The yield (the income as a percentage of the fund’s price) depends on the underlying yield of the bonds and the composition of the portfolio at any given time. When interest rates are low, corporate bond yields are low, and LKOR’s yield falls. When rates are higher, yields are higher. The fund’s yield is typically 50 to 200 basis points above a comparable US Treasury bond maturing at the same time, reflecting the additional risk of corporate default.

Because the fund tilts toward higher-credit-quality bonds, the yield is often somewhat lower than a traditional investment-grade index (which weights by market cap and thus favors larger issuers, not necessarily safer ones). However, the lower yield often comes with lower default risk, making it a potentially attractive trade for income-focused investors with moderate risk tolerance.

Duration and interest-rate risk

LKOR’s bonds have a weighted-average maturity of roughly 10 years, meaning the fund’s sensitivity to interest-rate movements is moderate to high. If interest rates rise 1 percentage point, the value of the fund’s bond holdings falls roughly 8–10 percent (a measure called duration). This interest-rate sensitivity is the largest risk LKOR faces—much larger than default risk in normal times. In a period of rising rates, LKOR will decline in value even if credit quality remains stable.

Risks and limitations

The primary risk is interest-rate risk. LKOR is a long-duration bond fund, meaning its price moves significantly with broad interest-rate movements. In a year when the Federal Reserve raises rates sharply, LKOR will likely decline in value, even if corporate credit quality is strong.

A secondary risk is credit risk itself. In a severe recession or credit crisis (like 2008), investment-grade bond defaults rise sharply. LKOR’s credit-scoring methodology aims to reduce exposure to the riskiest issuers, but no model is perfect. In a true catastrophe—a financial crisis that forces multiple large, previously stable companies into default—LKOR would experience material losses. The credit-scoring tilt reduces but does not eliminate this risk.

Liquidity is a third consideration. While the most frequently traded corporate bonds are liquid, some of LKOR’s holdings are less traded. If the fund faces heavy redemptions during a market panic, it may have to sell bonds at unfavorable prices or temporarily gate redemptions (temporarily preventing new share redemptions to preserve liquidity for remaining shareholders).

Finally, concentration risk can emerge. Corporate bonds are often concentrated in a few large issuers (Apple, Microsoft, Amazon, etc., if they issue bonds). LKOR tilts toward the safest issuers, which often means concentration in the largest, most-creditworthy companies. A shock to a single large issuer can move the fund’s price.

Who uses LKOR and how

LKOR is designed for income-focused investors with moderate risk tolerance—people seeking yields above Treasury bonds but unwilling to accept high default risk. Financial advisors use it as the “bond” portion of a balanced portfolio. A typical allocation might be 60 percent stocks (via equity ETFs), 30 percent LKOR or similar corporate bond funds, and 10 percent alternatives or cash.

LKOR is also used by income-focused retirees and endowments. Its monthly distributions provide regular income, and the credit-scoring tilt offers some downside protection versus a traditional bond index.

Tracking and performance

LKOR is not a pure index fund; it modifies the Bloomberg US Corporate Bond Index using the proprietary credit score. Performance comparisons typically pit LKOR against the Bloomberg index and other corporate bond funds. Historical performance shows LKOR’s behavior during rising-rate environments (when all long-duration bond funds decline) and during credit stress (when LKOR’s quality tilt often outperforms).

Expense ratio and costs

LKOR has a stated expense ratio (the annual management fee) typically in the 0.30–0.40 percent range—competitive with other corporate bond ETFs. However, the fund’s holdings require active rebalancing to maintain the credit-score weighting, and there are trading costs embedded in those adjustments. Over a full market cycle, the total cost of ownership is the stated expense ratio plus the friction from rebalancing.

Researching LKOR

The prospectus and fact sheet provide the core strategy and current holdings. FlexShares publishes detailed documentation of the credit-scoring methodology, allowing investors to understand what drives the tilts. Performance comparisons versus the Bloomberg US Corporate Bond Index and other corporate bond ETFs reveal the value (or cost) of the quality tilt in different market environments. Credit analysis platforms and bond research tools (CreditTrade, Refinitiv) offer bond-level detail and default-probability information. For a deeper dive, reading S&P and Moody’s ratings reports on LKOR’s largest holdings gives a sense of the underlying credit risks. As with any bond investment, interest-rate risk and credit risk are the two drivers of returns—LKOR cannot eliminate either, but its credit-scoring methodology specifically targets a reduction in credit risk relative to a market-cap-weighted index.