# Use of by/in for a line graph

Assuming I have to describe a line graph, which represents a trend in a past period of time and shows a declining line from A (value: 10%, year 1996) to B (value: 3%, year 2000), I could write:

1 After this point (A), figures decreased to 3% in 2000.
2 After this point (A), figures decreased to 3% by 2000.

Some part of me thinks they are both correct, but I can't avoid thinking somehow that the first line seems to lack the idea of a gradual progression towards the reached value. The mystery deepens since I have been coming across both the expressions to define the same behaviors for the line described.

What do you think?

By 2000 means from the time concerned (which you have not specified) to some (undefined) point in the year 2000.

In 2000 means in the course of the year 2000.

The meanings are completely different.

• Absolutely, i know they have different meanings, but maybe they are still both usable in this case? My thought was: if the declining line marks that value (3%) only in 2000, it is correct to say "it decreased in 2000 to 3%" (because before it was 2.9, 2.8, 2.7, and so on). But at the same time, I sense that if I write so, it can convey the idea that the decrease is not gradual, whereas I would give it better using "by". Commented Oct 14, 2022 at 16:14
• Ronald Sole is right. If there are no other modifiers in the sentence I would go with "by 2000". If suppose the sentence was "After this point (A), figures decreased to point B at 3% in 2000.", I suppose that could be used too. Commented Oct 14, 2022 at 16:53
• Ok I can agree, but I have found this sentence in my book for IELTS:"Following this [it was talking about 1950s trend], the number of cases dropped sharply to well below 20,000 IN the mid-1970s". It's from a description of a line graph. According to what both of you say, I would expect the use of "by". Commented Oct 14, 2022 at 17:13

"In 2000" merely says that the figures decreased and at some point in the year 2000, they were 3%.

"By 2000" adds the perspective of looking forward in time, from time A to 2000. If you say something happened "by 2000", you presuppose a previous point before it happened. It fits the narrative of first describing time A and then the status at a subsequent time.

Another example:

• In January, vaccines were/became available. (simply describes what happened in January)
• By January, vaccines were/had become available. (implies that it took time to reach this milestone, and it was reached during or before January)