Proportional progression (sitä mukaa kun)

Proportional Progression: sitä mukaa kun

To express that two continuous actions or changes happen at a proportional rate, use the conjunction phrase sitä mukaa kun (in proportion as, or simply as).

as / in proportion as (at the same rate)
sitä mukaa kun

Like "as" in English, it usually links a main clause and a subordinate clause, often sitting right between them.

The temperature rises as we excavate the bedrock.
Lämpötila nousee sitä mukaa kun louhimme kallioperää.
The conditions become more uncomfortable as we go deeper.
Olosuhteet muuttuvat tukalammiksi sitä mukaa kun menemme syvemmälle.

Clause Order

The subordinate clause starting with sitä mukaa kun can also be placed at the beginning of the sentence. When you do this, separate the two clauses with a comma.

As we excavate the shaft, we build support pillars.
Sitä mukaa kun louhimme kuilua, rakennamme tukipilareita.
As the groundwater rises, the cracks expand.
Sitä mukaa kun pohjavesi nousee, halkeamat laajenevat.

Matching Tenses

Because sitä mukaa kun describes simultaneous, proportional changes, the tenses in both clauses usually match. For ongoing progressions or general rules, use the present tense in both clauses.

The risk of collapse grows as the bedrock weakens.
Sortumisvaara kasvaa sitä mukaa kun kallioperä heikentyy.

For gradual changes that happened entirely in the past, both verbs often take the past perfect (pluperfect) tense.

As we had drilled the bedrock, the noise had worsened.
Sitä mukaa kun olimme kairanneet kallioperää, melu oli pahentunut.
As we had excavated downwards, the bedrock had become harder.
Sitä mukaa kun olimme louhineet alas, kallioperä oli muuttunut kovemmaksi.