Google has slowly but surely phased out its innovation-driving "20 percent time" program for the sake of productivity, reports Christopher Mims of Quartz

The program, which allowed employees to spend one day a week on creative side projects, led to the creation of signature Google products like Gmail and AdSense. In fact, the founders sang the project's praises in their 2004 IPO letter

"We encourage our employees, in addition to their regular projects, to spend 20 percent of their time working on what they think will most benefit Google. This empowers them to be more creative and innovative. Many of our significant advances have happened in this manner. For example, AdSense for content and Google News were both prototyped in '20% time.' Most risky projects fizzle, often teaching us something. Others succeed and become attractive businesses."

Mims, who spoke with former Google employees, reports that the first step of phasing out the 20 percent time was requiring engineers to approval from their managers to work on such independent projects.

Next, the upper management began to discourage managers from approving such requests. Since Google's managers are judged on the productivity of their team, it is in their best interest that their employees work on their primary tasks 100 percent of the time. 

This move fits in with bigger shift within the company, writes Mims. 

"The end of 20 percent time at Google fits with other moves made by CEO Larry Page since he took over in January 2011. Six months after he took the reins, Page announced that Google would adopt a 'more wood behind fewer arrows' strategy that would put more of Google’s resources and employees behind a smaller number of projects. This meant killing off Google Labs, which had previously been Google’s showcase for its experimental projects -- many of them products of employees' 20 percent time."

The end of 20 percent time won't be the end of innovation at Google, though: engineers will continue to work on new ideas, albeit in a more focused way, at Google X lab