Whats the design rationale behind putting the pagination of the bottom end of the search results?

If you look at the search results provided by Google and Bing,they have their pagination right at the bottom (after all the search results in a page are displayed)

I was just wondering about the design rationale behind that other than the fact that it would requires to look at all the search results before going on to the next page

Answer

We can use common sense to answer this question. Let's say you put pagination on the top of your SERP and it has 6 results, only 3 of which fit above the fold. This is the first SERP page:

________________
| 1 2 3 4 5 6 7 |
|               |
| Result 1      |

| Result 2      |
| Result 3      |
-----------------
. Result 4      .
. Result 5      .
. Result 6      .
-----------------

By putting the pagination on top, you are allowing the user to go to the second page without even considering results 4-6. There's a higher likelihood that the desired result is somewhere in 4-6, rather than 7-12, because search engines sort by relevance. There's no reason to skip a whole chunk of more relevant results just to search through less relevant results.

If, however, the pagination were on the bottom, there would be no gaps in the user's scanning. The user is forced to scan past all results on a page before going onto the next page.

________________
| Result 1      |
| Result 2      |
| Result 3      |
| Result 4      |
| Result 5      |
| Result 6      |
|               |
| 1 2 3 4 5 6 7 |
|_______________|

The fundamental design lesson to learn here is that you should position elements where they are most likely to be used.