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Prepositions after verbs

Increase in vs increase by

Use increase in for the thing that grows and increase by for the amount of growth.

Quick answer

How do increase in and increase by differ?

Increase in refers to growth within a category or area. Increase by gives the amount or degree of change.

There was an increase in demand.
Prices increased by 10 percent.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
increase in + noun

Naming what becomes larger

Use in after the noun increase or after forms of the verb referring to an area.

We saw an increase in traffic.
2
increase by + amount

Giving the size of change

By introduces numbers, percentages, or measurements.

Production increased by 500 units.
3
increase to + total

Giving the new level

To introduces the final amount after growth.

Sales increased to two million dollars.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
increase in
There was an increase in online sales.
growth within a category or area
increase by
Online sales increased by 15 percent.
amount of growth
increase to
The budget increased to $5 million.
new final level
increase with
Demand increases with population growth.
condition connected to growth

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using by instead of in after the noun increase

After the noun increase, use in before the category.

✕ an increase by costs ✓ an increase in costs

Confusing by and to

By gives the amount of change; to gives the final total.

✕ Profits increased to 8 percent. ✓ Profits increased by 8 percent.

Leaving out the amount after by

By should introduce a measurement or quantity.

✓ The temperature increased by three degrees.

Using in for percentages of change

Use by for the size of increase.

✕ Sales increased in 20 percent. ✓ Sales increased by 20 percent.

Quick practice

Choose the expression that matches the intended meaning.

1. There was an increase ___ fuel prices.
2. The population increased ___ 5 percent.
3. The budget increased ___ $3 million.

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Frequently asked questions

Can increase be both a noun and a verb?

Yes. You can say prices increased or an increase in prices.

What is the difference between by and to?

By shows how much something changed. To shows the final amount.

Do we say increase in or increase of?

Increase in is the standard modern pattern in most contexts.

identify-with-by-in-as, for "ignore by" or "ignore in"? illuminate by, with, at, for or in? "illustrate by" or "illustrate in"? "imagine for", "imagine by" or "imagine in"? imbue with, in, by or onto? immigrate to, from, in, with or into? impair by, for, in, because or throughout? "impart to", "impart in" or "impart by"? "impeach by" or "impeach for"? "impinge on" or "impinge upon"? "implement in" or "implement by"?

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