A new online service recorded its user growth over four years. In 2000, it had users. By 2005, the user count was . In 2010, it reached , and by 2015, it had users. Which of the following statements best describes the trend shown in the line graph representing this user growth? 
The user growth was linear over the four years.
The user count increased at an accelerating rate.
The user count increased initially, then decreased.
The user count increased, but the rate of increase slowed down.
The user count remained constant after an initial rise.
