MIKE ECONOMIC DATA
Personal Health Index — Rebuilt as PHI 2.0
For Release: July 17, 2026
Executive Summary
The Personal Health Index has been rebuilt. The original PHI was a simple monthly estimate — sleep, activity, and weight, often hand-tallied. With a complete daily record now flowing from Apple Watch, PHI 2.0 replaces it with a four-pillar, data-driven index graded against Mike's own baseline: 100 means "normal for Mike" (his 2023–2025 average).
This is a methodology change handled the way a statistical agency handles one: the old series is preserved intact as PHI-Classic, the new series is re-based to a documented baseline, and the two are shown side by side so the change is transparent. The headline number moves from PHI-Classic's 119.5 to PHI 2.0's 106.0 — that is a change of scale, not of health.
Key Highlights:
- • PHI rebuilt on daily Apple Watch data — four pillars: Recovery, Sleep, Activity, Fitness
- • Re-based so 100 = Mike's 2023–2025 normal; the latest reading is 106.0 (6% above baseline)
- • The legacy sleep/activity/weight index is preserved as PHI-Classic — no published number was rewritten
- • The series now reaches back to January 2023 (versus late 2025 before)
Old PHI vs. New PHI
Both series rise together out of the late-2025 trough — the level gap is the re-basing, not a change in health. PHI-Classic is shown on its own legacy scale. Both series are dated on the same one-month release lag, so a point compares the two indices over the same month.
Detailed Analysis
Old PHI vs. New PHI
Both indices tell the same story through late 2025 and 2026 — a dip into the winter, then a climb. They sit at different levels because they are measured on different scales: PHI-Classic on its own legacy baseline, PHI 2.0 re-based so that 100 equals Mike's 2023–2025 normal. The parallel trajectory is the point: the rebuild sharpened the resolution without inventing a different history.
One caveat on the comparison: PHI-Classic's February 2026 reading was never recorded — the published row duplicated March's value. Rather than leave a hole in the line, that point is shown as the midpoint of January and March (86.4) and is flagged as an estimate in the underlying data. It is the only interpolated point in either series.
Why the headline moved from 119.5 to 106
Nothing declined. PHI-Classic and PHI 2.0 are different rulers. PHI-Classic's 119.5 was a number on an open-ended legacy scale; PHI 2.0's 106.0 means "6% above Mike's normal," because the index is now anchored so that the 2023–2025 average is exactly 100. Re-basing to a fixed baseline is standard index practice (it is why the Consumer Price Index has a base year) — it makes every future number instantly legible: above 100 is better than normal, below is worse.
The four pillars
Recovery (30%) — heart-rate variability and resting heart rate: is the body rested and firing.
Sleep (25%) — hours slept and night-to-night consistency.
Activity (25%) — energy burned, steps, and exercise minutes.
Fitness (20%) — VO2 max and cardio recovery, the long-run cardio-capacity signal.
Each pillar is scored against Mike's own 2023–2025 baseline and combined by the weights above. A drop in the headline with Activity down tells a different story than a drop with Recovery down — and the quarterly notes on the series page say which.
What the rebuilt series shows
With history now reaching back to 2023, PHI 2.0 surfaces a real inflection: a decline through the second half of 2025 that bottomed in the fourth quarter — a period when a relocation disrupted the training routine — followed by a sharp recovery into mid-2026. Q2 averaged 106.93, among the strongest quarters in the series and just short of the 2023 and 2024 first-quarter peaks. Where a single month was extreme enough to hit the index's floor, the quarterly note says so, so the headline never understates a story quietly.
Reading PHI Going Forward
PHI is published monthly, rolled up quarterly, with a one- or two-line note on each quarter explaining the move. 100 always means Mike's 2023–2025 normal, so the number is comparable across time. The full method — pillars, weights, normalization, and the base period — is open and documented. PHI-Classic is preserved in full: plotted against PHI 2.0 in the comparison above, and published as `data/phi-classic.csv` in the open data repository. It is closed — no new PHI-Classic readings are recorded, and the series ends with June 2026.
Methodology & Data Sources
MIKE Economic Data tracks six indicators across productivity, financial, health, social, and intellectual domains. Raw data is collected monthly in CSV format, normalized against established baselines, and snapshotted quarterly for historical comparison. All source data and transformation logic is open-source and publicly auditable.
© 2025 MIKE Economic Data. All rights reserved.
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