Most discussions of ocean carrier reliability still revolve around a single question:
Did the vessel arrive on time?
That question is easy to measure.
It is also the wrong one for exporters.
Export execution happens inside the receiving window - the time period between Earliest Return Date (ERD) and the CY Cutoff. That window determines whether cargo can actually gate in, whether trucks are dispatched correctly, and whether a booking makes the intended sailing.
When that window moves, exporters feel it immediately - even if the vessel still arrives “on time.”
All terms used in this article - including ERD, CY Cutoff, receiving window, drift, and late-stage change - are defined in the Reliability Series - Methodology Appendix:
https://www.tradelanes.co/blog/reliability-series-methodology-appendix
This analysis is based on an observational system sample of executable export port-calls and is not a statistically randomized sample.
Filters applied (same as System Baseline):
Full methodology, thresholds, and definitions:
https://www.tradelanes.co/blog/reliability-series-methodology-appendix
A receiving window is considered moved if either the ERD or CY Cutoff shifts by one calendar day or more from its originally published value.
Plain English meaning:
MSC receiving windows are stable a majority of the time in this sample - but more than 4 in 10 port-calls still experienced a one-day-or-more shift. That is enough movement to create routine “plan breaks” even when arrival reliability looks fine on paper.
Drift measures how far an ERD or CY Cutoff moves between its original and final values, expressed in calendar days.
ERD drift distribution:
Plain English meaning:
Most MSC ERD changes are small. But the tail is not theoretical - about 1 in 5 MSC port-calls experienced 3+ days of ERD drift.
Static buffers are built for the middle of the curve. Operational pain lives in the tail.
Across the MSC sample, CY Cutoff drift exceeds ERD drift.
Average drift:
Threshold comparison:
Plain English meaning:
The exporter risk pattern holds here too: CY Cutoffs are the bigger execution constraint. ERDs can look manageable early, but CY behavior is what ultimately determines whether the plan still fits.
A late-stage change is a change to ERD or CY Cutoff that occurs within the final 72 hours before the receiving window opens.
Plain English meaning:
Nearly 1 in 4 MSC CY cutoffs changed inside the final 72 hours. That is the “dispatch lock” problem - the plan looks stable until the moment options are limited.
So far, we’ve looked at how windows move. Next, we look at where.
The Port Volatility Index (PVI) combines how far ERDs move, how far CY cutoffs move, and how often changes happen late, into a normalized score (0-10) that reflects how quickly static planning assumptions break at a port.
A higher PVI doesn’t mean a port is “bad.” It means static assumptions break faster there.
Below is a plain English interpretation of the ports with the highest volatility signals in this MSC sample. (Ports with small sample sizes should be interpreted cautiously.)
What this feels like:
At USLGB, MSC volatility is not subtle. Both windows move far enough that “standard buffers” stop being reliable. Planning needs range, not precision.
What this feels like:
This is a port where CY timing can change late and often. Even if averages look moderate, the late-stage behavior can force last-minute rework.
What this feels like:
A steadier profile - movement exists, but it is less extreme than USLGB. Exporters still need flexibility, but not constant re-planning.
What this feels like:
The magnitude is moderate, but a meaningful share of CY updates land late, which is where the real operational cost shows up.
What this feels like:
Low average drift but high late-stage signal in a small sample. If this pattern holds at scale, it is a “looks stable until late” environment.
What this feels like:
In this small sample, the late-stage signal sits disproportionately in ERD rather than CY. If validated with more calls, that would imply early acceptance timing is what breaks late.
Plain English meaning:
These events are not typical - they are stress tests that show how quickly drift can stack when multiple changes coincide.
Top examples in this sample:
Static buffers fail in these scenarios by design.
Plain English meaning:
If you plan MSC exports using only “on-time arrival” framing, you will still experience plan breaks. The movement rate tells you why: receiving windows move often enough that predictability must be managed explicitly.
Plain English meaning:
When drift has a long tail and late-stage changes are common, fixed buffers are routinely exceeded. Planning must adapt to observed behavior, not assumptions.
A vessel can be “on time” and still break export execution if the receiving window shifts underneath it.
This MSC edition shows:
Methodology and definitions:
Reliability Series - Methodology Appendix
https://www.tradelanes.co/blog/reliability-series-methodology-appendix
Next in the Carrier Reliability Series:
CMA CGM - publishing soon.