Last year the major search engine stopped providing the keyword data when they forwarded the organic users who clicked over from their search results page. what this means is that the site receiving the visitor no longer could determine the performance of users and the specific keywords they used on the search engine to get to the site. in other words, the site's visibility of visitor history was significantly decreased. what effect do you think this had on the volume of traffic?

This action by major search engine  would reduced the volume of traffic for site receiving the users from the search engine.

Explanation:

In order to get a better understanding of the answer above let first understand, what a keywords are.

Keywords are ideas and topics that define what the content of your website is about. In terms of SEO (Search Engine Optimization:it is the process that organizations go through to help make sure that their site ranks high in the search engines for relevant keywords and phrases) they're the words and phrases that searchers enter into search engines. These keyword are important because they are like a bridge between what people are searching for and the content you are providing to fill that need.

When this major search engine stopped providing this keyword data it meant that for those website who relied on those keywords to optimize their website in other to be top ranked on this major search engine and gain more traffic would no longer be able to gain access to these keyword and hence would fall in ranking on this major search engines and this in turn this would reduce the traffic to their website.