Hi Tessy,
Why don't you upload your graph? It's easy for others to comment when they see the graph :)
This data is comparingcompares the difference between developing and developed countries in the years 1990 and 1998 with the target of 100.
.... it's good to keep tense in simple present for this type of report writing
In cause of primary education, there was not much difference between the developing nations in during 1990 and 1998 and was below the target.
.... there is some issue with this line, but I cannot really comment without having access to your graph... Anyway I feel the latter part should be taken into a new sentence.
. In the same period, the developed countries also the number was roughly same, very close to the target.
what you've written has a grammar issue;
During the same period, the developed countries too had similar trend and statistics just reached the targeted figures.I guess I provided you with reasonable comments without seeing the graphs :) Try to upload them so that I can have another look :)