One of the more recent statistics emphasized by HLTV is KAST: % of rounds in which player x had a Kill or Assist or Survived or had his death Traded.

Not the sexiest opener, I know.

Anyways, KAST is an interesting yet seldom mentioned statistic, so we’ll talk about it here. One may wonder what exactly the point of KAST is; I reckon it’s supposed to measure the percentage of rounds in which you actually did something. It’s not far-fetched to posit that a round where you didn’t survive, you didn’t live, you didn’t get an assist, and you didn’t even get traded was not a great round.

KAST may be a good way of determining whether or not you did your job: an entry fragger may not want to die, but it is certainly expected, and his job is first and foremost to get traded once killed. If he does get traded, then he did his job. An AWPer may be tasked with watching a single angle; if the enemy team never come into his crosshair, he won’t get a kill, and thus this will also fail to show up on the stats sheet. In fact, the ADR of an AWPer watching a single uncontested angle will suffer in such a round. But of course the AWPer did exactly what was intended of him.

I find these two examples illustrative of the usefulness of KAST for the context at hand. ADR is a much greater (if imperfect) indicator of a player’s impact on the game. But in the case of impact, a player is never in sole possession of his destiny. If you’re a lurker and your entries can’t buy a frag, you won’t have much of an effect. The same goes for the poor souls that play B Mirage. Sure, you’re tasked with the retake, but if your teammates crumble at A without getting a single kill, you’re probably going to get stuck saving. Both these situations would reduce ADR, but they don’t ruin your KAST. After all, if you are on B and retaking is not an option, your new job is to survive. If you don’t survive, you didn’t do your job, in which case your KAST will suffer.

While the statistic can serve as an indicator of performance, it only does so in a binary way. Let’s say this is the argument for KAST:

∨ = and/or Q = In one round, Kill ∨ Assist ∨ Survived ∨ Traded = true. KAST: n of rounds Q/ n of rounds played P1: If Q, you did your job in that round. P2: If not-Q, you failed your to do your job in that round. C1: ∴ KAST is the percentage of rounds in which you did your job.

You’ll notice that while the result of KAST is a percentage, the particulars are not. The truth value of Q is binary, that is, there are only two possible results: =true or =false. Why is that a problem? Well, I doubt that many of us would think of ‘doing one’s job’ as an metric that can only be true or false. Surely, one can do one’s job well, and one can do one’s job poorly. Two people can do their job well, yet one can do it better than the second. This is the primary issue with KAST: Q measures whether you’ve done the bare minimum expected of you.

In other words, if Q obtains you haven’t been a net-negative player. The round considered holistically, you haven’t fucked up.

Clearly, however, KAST can only measure whether or not your value was negative. It may have been 0; it may have been an ace. In either case, Q obtains, and all rounds are equal under KAST. It cannot then be a nuanced measure of your level of performance, but only a measure of your round-to-round consistency: consistency in not fucking up.

I think this gets to the bottom of the C1.

You’ve probably been frustrated at the way in which I presented P1/P2. Specifically: what job? I’ll take some time now to expound on what this means. The ‘job’ that I take Q to measure is whether or not you achieved the minimum outcome you willed. If I’m holding an angle, my job as an individual within the game is to kill whoever comes on my screen, or at least survive. You may point out that, in terms of opportunity cost, merely surviving could be of negative value. Take, for example, a player whose team forced around his AWP. If he doesn’t get a kill, he had a negative impact on the round. Since Q is not sensitive to round-to-round context, it cannot account for this and thus fails, its true. In most cases, however, Q gets it right: you did the bare minimum.

Of course, this measures only a part of the player’s performance. It does not gauge whether or not your plan was a good one. If an AWPer decides to hold a passive angle when his team forced around him, he’s making a mistake. Thus Q measures only whether or not your plan obtained. It does not measure its quality. This is incredibly important when consider both AWPers and lurkers, since both risk surviving, but having no impact on the game. It is here that the opportunity cost is important: you may have a not-negative impact on the round, but you could’ve had a positive one had you had a better plan.

KAST, then, is a useful statistic to gauge a player’s level of consistent not-bad play. It does not, however, about for the goodness of that player, nor the goodness of his decision-making. Finally, it only accounts for not-bad rounds; it isn’t sensitive to bad plays. You may win a duel as a CT, a success, and overplay your hand by pushing forward, only to get picked. You have info, they have map control, so the impact isn’t clearly a net-negative, and thus Q triggers. At the margin, however, you made a net-negative decision between the first duel and the second. KAST does not account for this, and thus can in no way attest to the intelligence or scale of impact of the player it is measuring.

It’s still a handy thing to have of the scoreboard, I reckon.