When it comes to tracking economic momentum, quarterly changes in Purchasing Managers' Index (PMI) data provide valuable signals about GDP growth. My analysis of over 10 years of data reveals which PMI indicators are the most reliable for economic forecasting.
Manufacturing PMI: Moderate but Significant
Both ISM and S&P Global manufacturing PMI show statistically significant correlations with manufacturing GDP growth, with S&P Global slightly outperforming.
Manufacturing PMI Growth Correlations
Services PMI: The Superior Indicator
The services sector analysis reveals much stronger correlations. Given that services represent approximately 70% of US GDP, these findings have significant implications for economic forecasting.
Services PMI Growth Correlations
Key Takeaway
S&P Global Services PMI stands out as the strongest predictor, achieving what statisticians classify as a strong correlation (r > 0.7). Changes in this indicator can explain approximately 59% of the variance in quarterly services GDP growth.
Practical Implications
These findings suggest three practical strategies for economic analysis:
- Prioritize services PMI: The strong correlation between services PMI changes and GDP growth makes this a primary indicator for tracking real-time economic conditions. Focus especially on S&P Global Services PMI.
- Track quarter-over-quarter changes: A move from PMI 51 to 52 signals strengthening momentum more meaningfully than the absolute level. Focus on the direction and magnitude of change.
- Watch for divergences: When manufacturing and services PMI trends diverge significantly, it often signals sectoral shifts that may not be immediately apparent in aggregate data.
Bottom Line
Quarterly changes in PMI data provide statistically significant information about economic growth, with services sector indicators substantially outperforming manufacturing. The S&P Global Services PMI, with its 0.770 correlation, should be a cornerstone of any real-time economic monitoring toolkit.
Methodology
Data: Manufacturing GDP (FRED: VAPGDPMFG), Services GDP (FRED: SRVPRD), ISM and S&P Global PMI series
Approach: Monthly PMI converted to quarterly averages; Pearson correlations calculated between PMI changes and GDP growth rates (Q1 2015 - Q3 2025)


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