Nigeria might be Africa’s largest economy but it is increasingly home to one of the continent’s weakest passports.

Over the past decade, the Nigerian passport has suffered the worst decline in rankings on the annual Henley Passport Index with a 19-place drop. The decline in passport power now sees Africa’s most populous country rank 95th—firmly etched in the bottom quarter of the rankings. The drop in rankings also means Nigerian passport holders can visit two countries fewer now than they could in 2010 without first obtaining a visa.

Regionally, Africa accounts for four of the seven biggest drops in ranking on the index since 2010. Keeping with the historical trends, the region also dominates the bottom quarter of the rankings with only two countries—Seychelles and Mauritius—in the top 50.

In some cases, passport power is affected by local conflict and security fears as seen in the cases of Libya which has dropped 16 places since 2010 and Mali which has dropped 13 places. But, generally, the decline in the power of African countries is largely because countries in other regions are easing travel with reciprocity and boosting the strength of their passports at a much faster pace.

While Henley & Partners, the residence and citizenship consultancy that collates the index, notes a “substantial increase in the number of countries an average individual can visit without needing to get a visa in advance,” it also admits much of the progress on this front is firmly skewed towards holders of passports of developing countries. As such, the firm says the current global mobility gap is the “starkest” ever since the inception of the index.

Without the luxury of visa-free travel or even receiving visas on arrival, traveling abroad comes with the hurdle of expensive, paperwork-intensive visa application processes for a majority of holders of African passports. But most applications are likely to be met with rejection—sometimes without just cause: a joint All-Party Parliamentary Group report from British lawmakers in August showed Africans are being unfairly denied UK visas.

The real-life implications of difficult visa processes for Africans range from being unable to visit family members abroad to scuttling higher education plans. Up to 75% of African students who applied for study permits in Canada between January and May 2019 were rejected— far higher than the global rejection rate of 39%.

One easy way for African countries to boost the strength of their passports is by easing visa regimes on the continent. Yet, progress in easing travel between African countries remains slow-moving: 49% of countries on the continent offer neither visa on arrival nor visa-free travel to other African visitors.

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