If you’ve ever obsessively checked your email while awaiting a response or stressed over whether your electronic reply is too terse or longwinded, a recent study by the University of Southern California may offer some answers.

Researchers examined 16 billion emails exchanged among 2 million people over several months to learn more about email behavior. What they found could help you send better email and even know when to expect that response you’re waiting for.

Who responds to email fastest?

Researchers found that 90 percent of people replied to an email the same day it was received; however, some people are more likely to respond more quickly than others.

Teenagers reply the fastest, usually within 13 minutes. Adults between the ages of 20 and 35 are also fairly speedy; their average response time was 16 minutes.

But responses are slower for older age groups.

The average response time for someone 35 to 50 was 24 minutes, and people over the age of 50 took an average of 47 minutes to reply. However, those 50 and older also crafted the longest responses.

The study also found that men reply to email faster than woman — but not by much. A response from a woman took only about four minutes longer than one from a man.

People replying on a mobile device were twice as fast to respond as computer users, which the researchers note that variation could be because phones are often configured to alert people when new messages arrive. Replies via phone were also the shortest with a median length of 20 words versus 27 words by tablet and 60 words by computer.

new email notification on mobile phonePeople who set up email notifications on their mobile devices are more likely to respond to messages quickly. (Photo: Bloomua/Shutterstock)

When are you most likely to get a response?

Technology enables most of us to have access to email 24 hours a day, but just because we can reply to an email immediately doesn’t always mean we do.

The most common time to reply to a message is Monday through Friday during typical work hours. While some people will reply to weekend emails, as you’d expect, these responses tend to be both slower and shorter.

The very best time to send an email that you need a response to? A weekday morning.

And if you’ve been waiting for that reply for more than two days, it’s best to follow up. Researchers found that after 48 hours, there’s little chance of a response.

Should you read into that short reply?

It's common to want to read between the lines on the screen, and often a terse response can leave us wondering if the writer is upset with us. However, a short reply is typically nothing to worry about.

Emails that contain only five words are actually the most common, and more than half of email replies are fewer than 43 words.

If you're worried about the tone of an email you're sending, consider adding emoji or emoticons to help communicate your attitude.

How to know when the conversation is coming to an end

Email conversations tend to follow a pattern. In the beginning, the responses are similar in length, so typically if you send an email that’s several paragraphs long, you can expect the reply to also consist of a few paragraphs.

This tends to continue until about mid-conversation when emails grow shorter as the conversation begins to wrap up.

When there’s an abnormally long delay in response — if you’ve been replying back and forth on the hour and suddenly a day passes with no word, for example — the conversation is likely over.