Comparative Statics

"Ever wonder if the world would be better off without you… ?" Faced with such a troubling question from his best friend, Io couldn't help but retreat into the logical confines of the monetary world.

"Ever wonder if the world would be better off without you… ?"

Ryuu's voice was quiet and low, and had Io not been paying attention, he would have missed the comment. As he had heard it though, he tilted his head back, taking in Ryuu's unnaturally dejected expression as he slouched on the bench.

Io raised a brow. "That's an odd thing to ask. What brought this on?" The darkness in Ryuu's eyes lasted only a moment though, quickly replaced by indifference, as if he'd just asked about the weather.

"Nothing in particular. Just thinking out loud, I guess."

"That's a worrisome thing to be thinking about."

"Is it? I'm sure everyone wonders about it at some point," Ryuu's smile was bitter, telling Io that, no, this wasn't some spur of the moment angsty-teenager thought.

He thought Ryuu had been uncharacteristically quiet before. It was unusual enough for them to be spending a day together that could have been reserved for dates. The weather was nice and warm, perfect for that kind of thing.

And yet Ryuu had insisted on the two of them hanging out. Not the usual "coming over and playing video games" hanging out either. They'd gone to the park, ate crepes, walked around the city… if not for the fact that their conversations were the same as always, Io would have thought Ryuu was using him as a practice date.

But the whole time they were together, Io couldn't help but feel that something was off. It was only a feeling though, the kind he had no proof to act on, and so he tried to ignore it. But now, staring at Ryuu's slumped form on the bench by a vantage point overlooking the city, that feeling returned full force.

Io had no idea how to respond. Comforting people wasn't his strong suit, and if he thought about it, he didn't know have a model to look up to either. Out of all his friends, Ryuu himself was probably the one best at cheering people up; he did it for Io all the time, and not by doing anything special either. Io wouldn't have been able to mimic that sincerity, and even if he could, he doubted Ryuu's own comforting methods would be particularly effective on him.

Io thoughts drifted to En. He was always the most likely to first notice wistfulness, and dealt with it by giving the concerned party something else to think about. It was nothing more than temporary distraction, but sometimes that was enough.

But no, a statement like Ryuu's couldn't be laughed off and diverted to another topic. Even if it could be, Io didn't have a head full of trivia to bring up at times like this. The only thing in his head was numbers, financial statements, and business ventures. That kind of conversation would probably have just worsened Ryuu's mood further.

To Io though, there was something comforting about it. Faced with such a troubling question from his best friend, he couldn't help but retreat into the logical confines of the monetary world.

He sighed, having dragged on the silence long enough. "Do you want the short answer or the long answer?"

"Huh?" Ryuu looked up.

"The answer to your question. If the world would be better off without you?"

"Just forget it. It's not important."

"If it's something that has you making that face, I highly doubt that," Io told him sharply. Then in a softer tone, he continued, "Do you know what comparative statics are?"

"Some finance term?"

"Economics actually; it's the comparison of economic outcomes after a change in an exogenous parameter."

Ryuu rolled his eyes. "Great, now what's that in layman's terms?"

"It's the answer to your question. It's the effect on the world if we were to remove you from it."

Ryuu grimaced. "Is this the long answer? I vote for the short one."

Io shook his head. "The short answers is obvious enough, but it lacks the thought I've put into this." He walked over and sat down beside Ryuu. "I'll try not to make it too technical, so please pay attention."

"…Alright."

Io stayed quiet for some time, struggling to put his thoughts into words. "I guess the best way to think of this is to consider the world as an economic model. Its utility is how good it is, and everything in it is the factors that determine that utility. For simplicity's sake, let's just consider it to be some equation based on all the good and bad people have done up until this moment in time.

"Next we have to place you into this model. Zaou Ryuu, an average sixteen year old boy, one of 7 billion people in the world. You can think of humans as heterogeneous agents—each person's contribution to the world's utility is different, because each person's accomplishments are different. And then you can also consider that each person makes positive and negative contributions so we add the good ones and subtract the bad ones. In your case, I suppose you can think of making a girl feel special as a positive, and dumping her as a negative."

"Gee, how blunt of you."

"Right, so we will quantify all of the good and the bad you have done in your sixteen years of life and add it to the model as an exogenous parameter; a given that affects various others variables. Now the question remains, if we were to remove this parameter—you—would the world's utility go up or down?"

"And? What's your answer?"

"Zero."

Io didn't miss a beat with his response. Ryuu stared at him dumbfounded.

"Huh?"

"Ryuu, you are one of 7 billion people. You are sixteen years old, are known by a ridiculously miniscule amount of people in the world and haven't made any life-changing contributions to society. As far as the world is concerned, whether you're there or not makes such a tiny difference that it may as well be zero. It's neither better nor worse off."

"Oh, yeah, thanks a lot," Ryuu scowled and leapt from the bench, "I feel a lot better now."

"I wasn't finished," Io said coolly.

"Yeah, well—

"You were the one who posed this question; you may as well hear the rest of the answer."

"Fine, fine," Ryuu kept his back turned though, leaning on the railing and looking out into the city instead. Io knew he was still listening though, so he continued.

"Every one of the miniscule amount of people you know has their own utility curve and you are, of course, a factor in it. The more you spend time with a person, the bigger an influence you are on their personal happiness. I can't speak for anyone else, but I would say you are a direct factor on my utility."

Ryuu froze. He didn't turn around, but Io knew he was listening with bated breath.

"If we were to change that… if you weren't here, I would most certainly not be having this bizarre but oddly enjoyable conversation with you right now. That by itself is a minor thing, but you are my best friend and as such, there are countless of these "minor things" adding up to something significant. If, for any reason, there was less of you in my life, I can say with absolute certainty that my utility would decrease drastically and I would unquestionably be worse off."

Ryuu whirled around to face him. His eyes glistened. Io smiled warmly.

"Isn't that enough?"

AN: Thanks for reading!
(For the record, Ryuu did get the short answer. The long answer started giving me a headache so the Economics in this fic was simplified to a ridiculous degree... but the main point still holds!)
(My Econ textbooks are mocking me right now -.-")

Originally posted on Tumblr in response to the prompt: "Ever wonder if the world would be better off without you… ?" (Ioryuu) sen by an Anon. Thank you :)
(Also this is the last of the prompt fics)