Sequence of Returns Risk and Market Concentration

Week Ending March 13, 2026

Weekly Market Snapshot

U.S. equities finished the week lower as investors positioned ahead of next week’s Federal Reserve meeting while geopolitical tensions added pressure.

The S&P 500 declined 1.60%.
The Nasdaq Composite fell 1.26%.
The Russell 2000 dropped 1.79%.

Interest rates moved higher during the week, with the 10-year Treasury yield rising to roughly 3.50%. In commodities, oil prices continued to surge amid escalating tensions involving Iran, while the U.S. dollar remained firm against major currencies. Markets are now turning their attention toward the upcoming Federal Reserve meeting and any signals regarding the path of interest rates.

What Changed Beneath the Surface

The more important development this week was not the market’s weekly decline, but the continued shift in leadership beneath the surface.

All seven of the “Magnificent Seven” mega-cap technology companies are now negative for the year. Given their heavy weighting in the S&P 500, it is not surprising that the index itself has also turned negative year-to-date. This highlights a structural issue that often goes unnoticed during strong markets: concentration risk.

Over the past several years, a small number of large technology companies have driven a disproportionate share of index returns. When leadership becomes this narrow, portfolios that appear diversified on paper can still be heavily dependent on a handful of companies. The shift away from those leaders can have an outsized impact on index performance.

What This Means for Retirement Income Planning

Here’s where this becomes important for households that rely on portfolios for income or will soon.

When markets decline early in retirement, withdrawals can magnify losses. This is known as sequence-of-returns risk. The challenge is not simply that markets fluctuate. It’s that withdrawals during periods of weakness permanently remove capital that no longer has the opportunity to recover when markets rebound.

Concentration risk adds another layer to this dynamic. If a portfolio’s returns are heavily dependent on a small group of stocks, periods when those companies underperform can create sharper portfolio declines than expected. For retirees drawing income, that can accelerate the impact of early-cycle market weakness.

In other words, diversification is not just about owning many securities. It’s about avoiding hidden exposure to the same underlying drivers of return.

Takeaway

Markets often appear diversified during strong bull markets, but leadership concentration can quietly build beneath the surface. When those leaders eventually stall, indexes can fall faster than investors expect. For retirement portfolios, the real risk is not short-term volatility, it is being forced to withdraw income during those vulnerable periods.

The challenge in retirement planning is rarely predicting markets correctly. The challenge is understanding how timing interacts with withdrawals.

Stress-testing withdrawals through a sequence-of-returns risk model helps reveal how sensitive an income plan may be to early market declines. Structure not prediction, ultimately determines whether income remains sustainable through market cycles.