The Saudis.

The  surprising decision has caused a shock in business and official circles and in labor-exporting countries due to the  millions of expatriate workers in Saudi. Branches of Ministry of Labor and and  General Directorate of Passports of Ministry of Interior were overcrowded with 
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control of capital in the private sector. Citizens have become increasingly  reliant on the social and economic benefits provided by the state, and on the  other hand, state has become independent of society as oil revenues spared the  state the need of collecting taxes from citizens.

Thus, citizens. 

Thus,  over the years of the second oil boom, the percentage of Saudi workers to the total labor force accelerated downwards from  74.8% in 1975, to 47.3% in 1980, to 33.3% in 1990. By the dawn of the ninth  decade, with the decrease of oil price, increase of population, and inability 
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whiles citizens themselves find it greedy, opportunistic, and lacking proper  working conditions. As both sides this undesire, Al-Shihabi argues that GCC  governments opted to substitute its Arab employees in their bureaucracies with  citizens, with decreasing expenditures on developmental projects.

Oil 

Oil  price increase from $22 dollars in 1990 to its peak, $144 in 2008 which allowed for the accumulation of approximately $2  trillion available for use in mega projects, which promoted the private sector  to continue importing foreign labor, making the population growth rates in the 
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recommendations of International Monetary Fund and International Bank. One of  the characteristics that differentiates the foreign labor this time is reliance  on them by ordinary citizens as a source of income, not just major capitalists. 

With 

With  the saturation of the public sector, some citizens has opted for the private sector, not as employees but rather as  employers through renting multiple-story buildings and shops, trading of visas,  or working as a front image of establishments managed by expatriate workers, 
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many jobs occupied by the foreign labor.

Theoretically, economy?

Theoretically,  on the short-term, immigration or foreign labor decreases the wages of workers they are in competition with and  increases the wages of complementary workers.   Low-wages foreign labor increase competition on low-skilled jobs. In the  same time, high-wages local labor are benefited because they will pay less in  return of services that low-wages foreign labor provide, which enable them to  specialize in the jobs that suits their skills and educational levels.

For 

For  instance, the immigration of one million elementary-school-educated workers might result in a severe competition with  the elementary-school-educated local workers. In the United States of America,  for example, wages of high-school dropouts are negatively affected by