The recent ouster of Yousuf Reza Gilani as the prime minister of Pakistan continues a wearying pattern in that troubled country -- being the head of state or government of Pakistan may be one of the most insecure political jobs in the world.

Gilani himself might have seen the writing on the wall when he realized he was on the verge of becoming one of the longest-serving prime ministers in Pakistani history.

Officially, he served for 1,489 days -- from March 25, 2008 to April 26, 2012, the day the Supreme Court convicted him of contempt for failing to launch a probe against President Asif Ali Zardari for alleged corruption and money laundering.

(Gilani appeared to have almost a two-month grace period, until last week, when that self-same court ruled that he was unqualified to hold the office due to that prior contempt conviction).

Then, as the ruling Pakistan People’s Party scrambled to find a successor -- Zardari's first choice, a former minister named Makhdoom Shahabuddin, was ordered arrested by a judge in connection with illegal medical drug imports when he served as health minister.

This circus led to the nomination of Reza Pervez Ashraf, a former energy and water minister, who was approved by the parliament on Friday.

In the topsy-turvy world Pakistani politics, it was an unforgettable week.

Ashraf, assuming he is able to hold onto the job for any appreciable length of time, will be the 22nd prime minister in Pakistan since the country was founded in 1947 following the partition of British India into two nations.

However, it’s more complicated than that -- Benazir Bhutto served twice as prime minister (1988-1990 and 1993-1996), while her rival Nawaz Sharif served an amazing three different times.

(Had Bhutto not been assassinated in late 2007, she would have likely tied Sharif’s record for holding the top job on three separate occasions).

By comparison, over the same 1947-2012 period, India has had 17 prime ministers, with Indira Gandhi serving two separate terms. The United States, meanwhile, has had 12 presidents over that duration (with Dwight D. Eisenhower, Ronald Reagan, Bill Clinton and George W. Bush each serving full two terms).

In any case, the very first prime minister, Liaquat Ali Khan, who served a total of 1,524 days (roughly four years and two months), holds the record for the longest continuous tenure as Pakistan’s head of government. (Gilani would have at least tied Khan’s record, and perhaps broken it, if the Supreme Court had not been so eager to remove him from power).

On an aggregated basis, Bhutto and Sharif actually held the office of prime minister longer than either Khan or Gilani, but their various terms were interrupted multiple times.

The chaos and turbulence in Pakistan can also be illustrated by the fact that the job of prime minister was abolished on no less than five occasions – typically in connection with a military coup, the imposition of martial law, or by presidential decree. One of these periods lasted almost 13 years between October 1958 and December 1971.

This means that during the nearly 65 years of Pakistan’s existence, the country had no prime minister more than one-third of that time. Translated, on average, a Pakistani prime minister lasts in office less than two years – just one of the many measures of a country that is hopelessly unstable, corrupt and dominated by an ever-lurking military.

Under the terms of Pakistan’s constitution, a prime minister has a term of five years, but no one has ever finished such a period without interruption in office.

The “end” of a term can come in a variety of ways -- sometimes even by violence.

Indeed, the first prime minister, the aforementioned Liaquat Ali Khan, was assassinated in 1951 in an incident that remains mysterious as to motive and the lack of a proper investigation by police.

Zulfikar Ali Bhutto, perhaps the most dominant and well-known Pakistani prime minister ever, was forced out by a military coup and later executed in April 1979. His daughter, Benazir Bhutto, died in a hail of bullets almost three decades later while campaigning.

In most cases, the prime minister was dismissed or was forced to resign, typically after running afoul with the military or the president (or both).

One prime minister, Nurul Amin, served in office only 13 days in December 1971, on the brink of the civil war in East Pakistan which led to the independence of the new nation of Bangladesh. (Amin was a Bengali).

Now, one can only speculate how long Prime Minister Raja Pervaiz Ashraf will last in office. Not only does he face hostility from the judiciary and the entrenched military, but he also faces a host of legal issues himself, owing to alleged acts of corruption he committed while serving as a government minister.

If history is any guide, Ashraf should not get too comfortable in his office.