SOURCES, VERSIONS & WHAT CHANGED
2025 NADAC: weekly acquisition-cost changes
A year of weekly CMS acquisition benchmarks, with rate changes separated from repeated observations and file-coverage changes.
What is being compared
This is the first ACD NADAC release, prepared in October 2026 from the retained 2025 CMS annual source. The comparisons below are between adjacent weekly observations inside that source edition. They are not changes to ACD processing, differences between two purchased editions, or a new 2026 price series.
CMS’s dataset metadata was updated December 30, 2025; the final as-of date is December 31. Capture date, source coverage and rate effective dates remain separately recorded.
Changes across the year
These counts sum transitions across 52 adjacent pairs of weekly snapshots. The same NDC can contribute in multiple weeks. They are not counts of distinct drugs, launches or discontinuations.
| Comparison outcome | NDC/week transitions |
|---|---|
| Higher reported rate | 167,183 |
| Lower reported rate | 175,308 |
| Changed unit, pharmacy type or rate classification | 3 |
| Other changed source attributes | 12,796 |
| Present after absence in the preceding snapshot | 3,393 |
| Absent after presence in the preceding snapshot | 3,087 |
| Unchanged comparison fields | 1,219,540 |
Effective dates and units
The source contains 171 observations with rates effective after their snapshot date. They remain in the download with explicit flags. Every comparison retains both effective dates: a changed reported rate is not necessarily a price event occurring that week. An identical rate can be carried forward into a later weekly file.
Rates are USD per each, milliliter or gram. Quantitative changes require unchanged pricing unit, pharmacy type and rate classification. No mean is taken across incompatible units, and missing snapshots are not filled or bridged.
From change sheet to analysis
changes.csv identifies the affected NDCs and original rows. weekly_summary.csv supplies the breakdown by week; ndc_summary.csv describes each NDC’s observed span and gaps. All 1,608,416 original source rows are retained in observations.csv. The Python guide shows an endpoint comparison using real sample records.
Sources and purchase
Source: CMS NADAC 2025, published as public-domain data. CMS’s pricing methodology includes a three-month moving average for generic rates from December 18, 2024. ACD preserves those values. These are surveyed acquisition benchmarks, not patient retail prices or reimbursement guarantees.
The prepared annual edition costs $29 once. Improvements to our processing of these retained inputs are included; later source editions may be separate purchases. Inspect all fields, files and samples · Download the summary data.