[QUOTE=Kamyar;8309]This is from
1993. I don't know the statistics now, but I know that the number of Uzbeks has decreased in Tajikistan.

[/QUOTE]
I think the fertility of Tajiks was very similar to uzbeks during last decades. most probably that the increase in percentage of tajiks in Tajikistan has nothing to do with fertility. The reason might be another.
The thing is both in Uzbekistan and Tajikistan there is no clear border between "Tajiks" and "Uzbeks". Especially between "northern" tajiks (Bokhara, Samarqand, and Khojand), and uzbek population of traditional cities of Uzbekistan like Kokand, Andijan, Termez etc. There was dynamic process of persization, turkization, repersization and returkization in the region during last at least millenium. The result is you can find total regions in the area where people speak Persian, but have substantial turkic biological heritage as well as regions where people are mostly iranians by biological heritage but speak Turkic. The population of primary turkic-speaking Kokand city (in Perdian "Hooqand") very often point out that they are in fact tajiks, while Persian-speakers of Khojand can easily switch into "uzbeks" when they need to visit Uzbekistan. If tomorrow something happens in Uzbekistan and the Uzbeki government starts the politics of persization, i believe 90% of uzbeks start calling themselves "tajiks". Same thing may happen in a number of regions of Tajikistan, especially in Soghdian province - i think 90% of Persian speakers might turn to be "uzbeks" if there will be corresponding political and social environment.
that's why the amount of uzbeks has decreased in Tajikistan during last decades from more than 20% to less than 15%. it's similar to how the amount of Tajiks has decreased dramatically in Bukhara and Samarqand at early 20 century when "tajiks" has become insignificant minority from absolute majority in those cities.