LinkedIn is the biggest professional network all over the world. LinkedIn's stock is very volatile and historically it's very difficult to define the trend. Since August the stock grew up more than 40%, however YTD return is just around 3.8%. What is behind such a significant fluctuations this year? To answer that question I would like to check the company's operating and financial metrics according to the latest filling. Revenue LinkedIn is increasing its revenue. For nine months ended September 2015 the company's revenue grew up 35% compared to the same period last year. Most of this growth came from several things. One of them is growing number of customers. Another one is effective acquisitions. One of the examples of successful acquisitions is the deal with lynda.com. Learning section contributed more than $60M in revenue for nine months this year and more to come. Number of customers, users As soon as LinkedIn combines both B2B and B2C segment, the company receives its revenue from its users for premium memberships and from companies for different services such as hiring, learning etc. As the company noted in its latest 10-Q filling, 75% of talent solutions revenue comes from B2B segment. They call it LCS or LinkedIn Corporate Solution. The number of both private and corporate clients grew up 19.5% and 31% relatively. ARPA Average revenue per account is growing as well. The ARPA for private clients grew up 9.7%, while the ARPA for corporate clients grew up 6.8%. I think that this is quite a stable high growth rate that shows that the whole company is growing really fast. Cost of revenue Cost of revenue increased as % of revenue from 24.15% as of September 2014 to 26.71% as of September 2015. I assumes, that the distribution of cost of revenue is approximately the same as the top-line revenue. If we calculate the cost of revenue per user, we'll get the growing trend for both corporate and private clients. And the growth of cost of revenue per user is twice higher than the growth of ARPA. That's not a good sign for the whole business. Operating expenses Sales and marketing expenses grew up as well: 64.2% as of Sep-2014 against 67.4% as of Sep-2015. As soon as this type of costs represents the highest share of revenue, I checked the sales and marketing costs per user. And again, both business divisions (private and corporate) grew up as well: 11.5% for private clients and 8.7% for corporate. Research and development expenses grew up as well. To summarize, the company is growing, but it slightly kills its operating efficiency. What do you think about LinkedIn stock perspectives?