Pakistan has seen, Three Versions of Quota System.

First one Quota System was introduced in Sept 1948, it used a Regional/Provincial model for recruitment in Govt Jobs and accordingly;

Bengal 42%

Punjab 23%

Potential Immigrants from India 15%

Karachi had a 2% separate Quota

All Other provinces [Sindh, Balochistan and NWFP] and Princely States had a 17%

This was then revised in Nov 49 and now instead of using the term Potential immigrant, merit was used and new quota was;

Merit 20%

Karachi 2%

Bengal 40%

Punjab including Bahawalpur 23%

All other 15% [Sindh, Balochistan and NWFP]

Under the 1956 constitution, its scope was up till March 71. That is for 15 years.

1962 's constitution reduced the term for 10 years, that is till 72. So actually extended the term by a couple of months.

71 and subsequent breakup of Pakistan changed not only the demography, but also the weightage in terms of population shift.

Sindh started showing a heavy Urban/Rural divide as an ethnic divide between Sindhis nearly all rural and Muhajirs nearly all Urban.

The new percentages according to the changed realities was then

Merit 10%

Punjab 50%

NWFP 11.5 %

Balochistan 3.5%

FATA 4%

Azad Kashmir 2%

Sindh 19%, subdivided using a 60/40 formula of Urban/Rural division into 11.4 Rural and 7.6 Urban.

The actual Percentage of Urdu Speaking Hindustani Mujahir in the population of Pakistan is 7.6%, they are 19% of Sindh's Population, even then the  60/40 parity gave the advantage to them.

The First Quota System was implemented by Liaqat Ali Khan, it was for 25 years, that is upto Dec 72.

Three full provinces Sindh, Balochistan and NWFP were given 15% Quota and Urdu Speaking Hindustani Mujahirs alone were given 20% in the name of  "Merit " and  2%  for Karachi alone, that makes it  22%.

Ironically, the 15% Quota of Sindh, that too normally went to Urdu Speaking Hindustani Mujahirs, due to their settlement in the cities and towns of Rural Sindh.

Christina Lamb  put that figure as high as 40%. Whereas, some other researcher like, Dr Hasan Askari had put that figure close to 65% jobs in Govt Services went to Urdu Speaking Hindustani Mujahir.