XLK vs XLC — Quantitative ETF Study

Research Background — The 2018 GICS Reclassification

In September 2018, S&P and MSCI implemented a significant revision to the Global Industry Classification Standard (GICS), creating a new sector called Communication Services and transferring a number of large technology-oriented companies from the Technology and Consumer Discretionary sectors. The primary transfers relevant to this study were Alphabet (Google) and Facebook (Meta) from Technology to Communication Services, and Netflix from Consumer Discretionary to Communication Services. This reclassification simultaneously removed these companies from XLK and added them to the newly reconstituted XLC (previously the Telecommunications sector ETF). The study analyzes the statistical properties of both ETFs across the 8 observable years since XLC's relaunch in June 2018.

Constituent Holdings Analysis — XLK vs XLC

The table below compares the top constituent holdings of each ETF. The structural divergence is clear: XLK concentrates in semiconductors, enterprise software, and device hardware, while XLC concentrates in digital advertising (Google, Meta) and digital media (Netflix, Disney). Despite this compositional difference, macro correlation is 0.927.

Approximate weights as of 2025. Holdings change with market capitalization movements and index rebalancing. Zero holdings reflect GICS sector classification rules.

Annual Return Comparison — XLK vs XLC (2018–2025)

N=8 annual observations. XLC launched June 2018; 2018 is a partial-year starting mid-year but treated as annual for consistency with other studies. QQQ shown as reference series.

Compound Growth Index — $1 Invested January 2018

$1 rebased to January 2018. XLC's -37.6% in 2022 drove the primary terminal value divergence from XLK.

Full Statistical Summary — 8-Year Back-Test (2018–2025)

All metrics computed over 8 annual observations (2018-2025). XLC's weaker risk-adjusted performance (Sharpe 0.411 vs XLK 0.748) is primarily attributable to its deeper 2022 drawdown driven by Meta's -64% return that year.

Correlation Analysis — Why High Holdings Concentration Doesn’t Reduce Co-Movement

The macro driver argument

The intuition that XLC's distinct holdings (Google, Meta, Netflix) should produce meaningfully differentiated returns from XLK is undermined by a more powerful force: both ETFs are driven by the same macroeconomic factors. Interest rate expectations affect growth stock valuations uniformly across Technology and Communication Services. AI investment cycles benefit Nvidia (XLK) directly while also lifting Google Cloud and Meta AI spending (XLC). Digital advertising revenue is tightly correlated with semiconductor earnings cycles because both depend on the same enterprise technology capex and consumer confidence dynamics.

The 2022 evidence

In 2022, when the Federal Reserve raised rates by 425 basis points, XLK fell -27.7% and XLC fell -37.6% — both large, directionally identical, and both driven by the same rate-sensitivity mechanism. XLC's deeper drawdown reflected Meta's -64% decline (an idiosyncratic factor related to Reels investment costs and TikTok competition) rather than any structural difference in interest rate response. This episode confirms that the two ETFs share a correlation regime even when specific constituent performance diverges significantly within that regime.

Portfolio construction implication

A 0.927 correlation between XLK and XLC implies that a portfolio holding both allocates approximately 92.7% of the combined position to the same underlying return factor. Only 7.3% of the combined exposure is statistically independent. For practical diversification purposes, investors seeking Google and Meta exposure alongside XLK's Technology holdings should consider QQQ, which includes all of these names with a single 0.977 correlation to XLK — providing essentially the same concentrated growth-tech exposure in one instrument.

Annual Return Data — Full Observation Set (N=8)

XLK outperformed XLC in 6 of 8 observable years. The primary driver of XLC underperformance was Meta's extreme volatility (-64% in 2022, +197% in 2023) which distorted XLC's return distribution.

Estimated Pre-2018 Performance — Back-Projection Methodology

Because XLC did not exist before June 2018, estimating its historical performance requires a proxy methodology. Given that Alphabet became publicly traded in 2004 and Meta in 2012, a reasonable proxy is constructed as a weighted blend of XLK and the S&P 500 total return index, with the XLK weight increasing over time as Google and Meta grew to represent larger proportions of what would have been XLC's portfolio.

Using this back-projection, estimated XLC 2004–2025 CAGR is approximately 10.9% — below XLK's actual 14.25% CAGR over the same 22-year window. This further supports the finding that XLC does not offer superior return potential versus XLK as a growth-technology instrument, even with Google and Meta as major holdings.