 So, measurement of permanent, that was not a permanent product. Measurement by, well, actually it is because it's already been recorded. So measurement by permanent product, we're going to make a whole bunch of errors and make this measurement, again, measurement by permanent product. I've made two errors so far, I don't know, 753,243,337.4, see, exactly. So permanent product, did you measure something that was left behind? So I signed my name, I wrote something on a piece of paper, I solved a math problem on a piece of paper, I gave you a cookie, something. You know, some product has to be left behind to be counted, right? That's a measurement by permanent product procedure. It's really awesome because it's easy to establish inner observer agreement, because there's a permanent product, you don't have to go, did that happen? No, did it happen? No, it happened, no, it didn't happen. I think it happened, you didn't think it happened. What the fuck, you're all fucking wrong. With permanent product, you don't have to worry, see, it happened. So there's two, permanent product, something was left behind and you count those things that were left behind.