Studies showed that results are not correlated to ads spending:
AdGooroo Kantar Media1 analyzed search advertising activity in 10 different business categories on Google AdWords in the U.S., U.K. and France during January 2014 and found that only 1% of search advertisers generated an average of 80% of estimated paid search clicks across all categories (CPC).
56% of online ads are not seen by internet users (Google analytics2)
Even though the online ad market provides opportunities of growth especially for mobile ads spending, a study showed that the less appreciated ad formats for French and American internet users were the ones of mobile applications, social media and search engines. Only 3% of users would rather see an ad on social media including 1% on mobile application compared to 75% of them for TV shows and print magazines (Adobe, “State of online advertising study 2012).