YouTube is by far the most popular user-generated video site on the web but according to a new report, the Google-owned property isn't making near as much money as some analysts had hoped for.

Two anonymous sources recently told The Information that YouTube brought in $3.5 billion in advertising revenue last year. After paying content partners, that figure dropped to just $1.5 billion. While those are solid numbers by some standards and YouTube is profitable, it represents just a tiny amount of Google's overall income.

If the figure is accurate, it would account for just seven percent of the $58 billion the search giant brought in 2013.

YouTube revenue is an area that Google is certainly interested in improving as evident by the appointment of former AdWords and AdSense boss Susan Wojcicki to CEO a few months ago. Part of her duties will no doubt be to improve the site's revenue moving forward.

Another area that YouTube is reportedly focusing on is monthly video viewing hours. Before former YouTube CEO Salar Kamangar departed, he set a goal of growing this metric from a base of 100 million monthly video viewing hours in 2012 to 1 billion in 2016. At present, the site averages around 300 million monthly viewing hours.

There's still a lot of work left if the company wants to reach the goal by its target date but with more and more people getting online each day, it certainly seems plausible.