According to wikipedia Facebook has 55 million active members. With 6 billion people in the world, this is a little less than 1%
According to this article: http://searchengineland.com/bing-reaches-20-percent-search-milestone-in-us-market-218574 In April 2015, Yahoo had 12.7% then.
In past, users of yahoo in good quantity. At that time there is no concept of android system or OS. At that time when Yahoo messenger was used by people yahoo is reputable forum. But now after progress of network industry and Android by google suddenly the users grow alot. At this stage google lead the world as well as SEO. I think a day will come when google takeover yahoo.
Most of the people are generally using google+ then yahoo. they preferred google rather than yahoo.Very less percent of people use yahoo.Atleast 5 to 10% of people use yahoo as their search engine
Can you define that 5% more - are they likely to be a particular age, with a partner ISP (like Xtra in NZ) or from a particular country?
In honesty, I'm not sure the exact percentage but one thing I do know for sure if that I wouldn't be planning any of your business around the long term success of Yahoo. With varizon taking over and the constant changes in the company I just see it as a dying trend personally. I'm putting money on the fact that when the takeover happens less and less will be focused on search as it's not generating them enough money, so anyone who does still use Yahoo search probably wont be in the coming years. The company is dying IMO.