### Introduction

In the previous quarter ending September 30, 2014, Twitter revealed that they had 284M users[1]. This led many to speculate that Twitter could reach 300M active users as early as the next quarter ending December 31, 2014[2]. This became an especially important target when Instagram announced December 10, 2014, that their Social Network had reached 300M active users[3], making it effectively larger than Twitter. Twitter is expected to report its next quarterly earnings on February 5, 2015 when we will know for sure. In anticipation of the quarterly announcement, I have analyzed data from Twitter over the past year to measure what their quarterly MAU will be.

### Methodology

Twitter defines Quarterly MAU as “Twitter users who have logged in and access Twitter through our website, mobile website, desktop or mobile applications, SMS or registered thirdparty applications or websites in the 30-day period ending on the date of measurement.” As a proxy measure for logins, I use posting activity. While not every Twitter user posts, the percentage of Twitter users who do post is likely fixed. Growth in posting activity quarter over quarter is proportional to growth in logins, and hence MAU.

To measure posting activity, I created a sample[4] of 6,355 accounts that posted at least once between September 1, 2013 and December 31, 2014. My sample size was 12,540 individuals, which would give me an estimate accurate to 1% with a 95% confidence, which means that I would likely measure the same number 19 out of 20 times. During the period of study, I created 30-day windows and counted how many accounts in my sample tweeted during that time. I averaged the number of accounts tweeting in each time window where the period ended within the quarter to get an average number of accounts tweeting in a given quarter.

Since my raw numbers are just a sample of the Twitter population, I needed to determine the factor to scale from my sample to the actual MAU reported by Twitter. To do this, I used a second order polynomial model to fit my measured data to Twitter’s reported MAU using a least squares method.

### Results

Figure 1 shows the resulting forecast for the Twitter Quarterly MAU in the Quarter ending June 30, 2014. My forecast puts the MAU at 300.0±6.2M. The most optimistic forecast puts Twitter at 306M MAU. And there is a chance that Twitter won’t crack the magic 300M MAU barrier, coming in as low as 294M.

Figure 1: Forecast of Twitter MAU for Q4 2014

What is intriguing is that the average of the forecast is exactly at 300M MAU. This gives exactly a 50-50 chance that Twitter meets or exceeds 300M MAU. My previous forecasts, while accurate within the statistical error, have underestimated Twitter’s official results[5]. While there is no analytical reason to pick one outcome over the other, my money is optimistically on Twitter blowing past the 300M mark!

### Post Call Discussion

February 5, 2015, Twitter released they’re quarterly numbers. The official MAU was 288M. This number is quite low compared to my forecast — it even failed to fall in the expected range. But there was one interesting caveat on the number Twitter reported.

In the fourth quarter they took a “write down” of “approximately 4M net net Monthly Active Users in the fourth quarter due to changes in third party integrations.”[6] Twitter does not provide more information what this means. I think this probably represents a one time adjustment in their reporting. If that is the case, the unadjusted number would be 292M. This number is closer to the lower range of my model’s estimates.

Featured Image courtesy of Wikimedia Commons, the free media repository