When severe flooding in Pakistan left millions of people without food, shelter, and water, I wrote a post wondering why that disaster was getting less attention than Haiti’s earthquake. I suspected the gradual nature of the disaster was part of the problem, and commenters had additional suggestions, ranging from Haiti’s closeness to the US to the US public’s overall view of Pakistan as a nation.

Last week, The New York Times’ Lydia Polgreen put some numbers on the Haitian earthquake vs. Pakistani floods comparison and delved into reasons for the disparity:

In all, $3.4 billion has been collected for the victims of the Haiti earthquake as of October, with more than $1.1 billion coming from private donations, according to figures compiled by the United Nations. Close to $1.7 billion has been pledged for Pakistan, but less than $300 million came from private donors. The United States government pledged almost one-third of the total.

Humanitarians have long struggled with this paradox. The number of dead, along with the swiftness and drama of their demise, trumps almost any amount of agony among those who survive a disaster, particularly a creeping one.

“Donors use the number of deaths as a barometer with disasters,” said Randy Strash, strategy director for disaster response at World Vision. “When you have a slow-onset disaster, like the flooding in Pakistan, which accumulated for three weeks and sustained for much longer, you don’t have that same shock value.”

So, would an earthquake in Pakistan have spurred the same donor generosity that the earthquake in Haiti did? Polgreen points out that when an earthquake struck the Pakistan-controlled portion of Kashmir in 2005, donors responded generously, giving what amounted to $570 for each quake-affected victim. The per-victim count for the flood is just $40. That stark difference demonstrates just how irrational we are with our giving:

The fact that individual donors have seemingly irrational reasons for giving to one disaster and not another demonstrates how counterproductive the current methods of raising money for humanitarian relief are.

“It is a little bit like funding your local fire engine by rattling a tin on the street every time a fire breaks out,” said Peter Walker, an expert on humanitarian aid at Tufts University.

What is more, the giving public perceives natural disasters as sudden shocks that require an immediate infusion of cash to get life back to normal, and that once the initial shock is over, the affected country continues on the same trajectory, Mr. Walker said. This might be true for wealthier countries — the earthquake in Chile, for example, caused widespread damage but was unlikely to alter the overall future of the country.

But in poorer countries like Haiti and Pakistan, a major disaster fundamentally changes the equation, and their needs are both immediate and long term.

“For countries low down on the development scale, these disasters can drastically change the development curve,” Mr. Walker said. The result is a long-term need for the kind of humanitarian aid that the public gives only in the teeth of a major disaster.

Of course, it’s important to differentiate between gifts from individual donors and aid from other countries’ governments. Individuals giving $20 or $50 might be moved by what they’re seeing on TV (Polgreen also notes that US reporters gathered a wealth of moving footage from Haiti, but less from Pakistan). Governments, we hope, will consider the number of people affected, the severity of the damage, and local institutions’ ability to respond. Pakistani journalist Ahmed Rashid also reminds the international community that if Pakistan can’t recover from the floods, it risks becoming “a failed state with nuclear weapons.”

Now Haiti is facing a cholera epidemic. As with Pakistan’s flood, the toll will rise week by week, and the disaster won’t be over any time soon. The fact that the country so recently suffered a devastating earthquake might make this epidemic feel more like an emergency, and spur individuals to give again.

It’s also worth pointing out that cholera has killed more than 1,500 people in Nigeria over the past few months, and the disease has also spread to neighboring Cameroon, Chad, Niger, and Benin. The Guardian article that alerted me to this alarming development didn’t mention anything about donations being sought or received to address the outbreak.