Some jurisdictions report nearly complete results within hours while neighbours take days. The difference is procedural rather than technical or political.
Processing is separate from counting
A mailed ballot arrives in an outer envelope carrying a signature and identifying details. Before the ballot can be counted, that envelope must be verified and removed.
Verification, opening, flattening and sorting is labour-intensive work, and it is entirely separate from feeding the ballot through a tabulator.
Where election officials may begin processing weeks in advance, the counting itself is quick once polls close. Where they may not, everything happens at once.
The rules differ for reasons that predate mail voting
Restrictions on early processing generally exist to prevent partial results leaking before polls close, a concern dating from an era when mailed ballots were a small share of the total.
When mail voting expanded, some jurisdictions revised those provisions and others left them untouched, which is the immediate source of today's wide variation in reporting speed.
Changing them requires legislation rather than an administrative decision, so the rules move only when a legislature has both the time and the appetite for the subject.
Order of reporting creates apparent swings
Different voting methods are counted at different times, and voters using each method are not politically identical. Early in-person totals can look unlike late mail totals.
The result is a count that appears to shift steadily in one direction as the evening proceeds, even though no individual ballot changed.
Whether the shift runs one way or the other depends on which category a jurisdiction happens to tabulate first, which is a scheduling decision.
Cure periods extend the timeline deliberately
Many places allow a voter whose signature did not match to correct the problem within a set window, so that a clerical mismatch does not discard an otherwise valid ballot.
That window necessarily runs past election day, which means a complete count cannot exist until it closes, regardless of how efficiently the counting office is run.
Military and overseas ballots work similarly. Postmark deadlines allow them to arrive after election day, and a close contest can remain genuinely undecided until those envelopes are in.
Speed is not the only design goal
Faster reporting can be bought with earlier deadlines, fewer cure opportunities and less pre-certification auditing, each of which trades accuracy or access for time.
Jurisdictions weigh those trade-offs differently, and the resulting spread in reporting times reflects genuine policy choices rather than differing competence.
Certification deadlines, which fall weeks later everywhere, are the point at which results become official, and they are far more uniform than election-night reporting is.