Dear Muna;
I stopped by your fruitful post and wanted to join the discussion, I think there could be many reasons behind that some causing males not get married and some causing females to accept to be the 2nd wife:
Female population: "I tried to find up-to-date censuses records"
Women outnumber men
Some statistics from worldpress
Population: 36,080,373 (July 2001 est.)
Age structure: 0-14 years: 44.62% (male 8,227,011; female 7,870,783) 15-64 years: 53.29% (male 9,619,218; female 9,608,469)
Having in mind that the Net migration rate is very high
Poverty
Over 90 per cent of the Sudanese people (according to some estimates) live below the international poverty line (surviving on less than $1 per day). UNFPA
A lot of young males can’t afford to get married, and many older can afford it for the second and third time.
Aging factor
Many of us (males) start thinking about marriage when they get above 30 and some time even in the 40’s, vs. that our sisters are getting married in their 20’s and 30’s and some even before that.
Migration
Some of our young men started to get married where they landed because it is not expensive and to get legal status
Social Issues
Some (not that many) get the second (or 3rd or 4th) wife for some social issues (too many to mention).
Some women accept that for the above reason and add to them:
Family restrictions
A way to help the family
To Avoid remaining lonely
Some cultural prospective regarding unmarried women at a certain age (we can’t deny that)
I hope I added some to your post.
mohamed elbashir