For months, markets have been jittery about the amount of money tech companies are spending on artificial intelligence. To tell us more about what is rattling the markets, we're joined now by NPR tech correspondent John Ruwitch. SUMMERS: So, John, we have heard from some major tech companies this week about their AI spending as they put out their quarterly earnings reports. Microsoft, Meta, Qualcomm and, today, Amazon are just a few of the big-name companies who've been reporting quarterly earnings this week. RUWITCH: Well, there's been a brutal AI sell-off of tech stocks in South Korea, which has some very important tech companies like Samsung and the memory chip maker SK Hynix.