After Exxon Mobil (XOM) posted weak second quarter earnings last week, online marketplace Amazon and social media company Facebook slid past the oil giant, taking the position of fourth and fifth largest U.S. traded stocks by market cap behind Apple (AAPL), Alphabet (GOOGL), and Microsoft (MSFT). That came after the two tech companies made their way past Berkshire Hathaway last week—signaling how much investors expect the two tech giants to grow, and marking the ascendency of tech companies.

While both Exxon Mobil and Berkshire Hathaway’s (BRK-A) shares rose in comparison to a year earlier, those gains were outstripped by the rapid growth of Amazon and Facebook’s stock. Over the course of a year, Amazon gained $113.2 billion in market cap to $363.9 billion, while Facebook rose by $91.9 billion to $356.9 billion. That put Facebook just a sliver above Exxon’s $356 billion market cap.

Investors clearly have lofty expectations for the two companies, and especially for Amazon. The online marketplace now claims a whopping price-to-earnings ratio of 189.1. Facebook has a p/e ratio of 59.5. In comparison, Apple claims a ratio of 12.3.

Those expectations were fanned by stream of good news released by the two titans over the past few quarters, even as their peers and competitors such as Apple and Twitter languished. Amazon recently posted record profits for a third straight quarter, while Facebook once again produced earnings that were much higher than expectations on strong mobile ad sales.

Meanwhile, shares of Exxon Mobil and Berkshire, two much older companies in more mature markets, have been struggling. ExxonMobil’s stock has stood up remarkably well despite the plunging price of oil, and a Berkshire Hathaway that wrestled with volatile markets and a tepid economy.

That said, while investors might be giving the signal that Amazon and Facebook are more valuable than Exxon and Berkshire, the two tech companies still lag behind the oil and insurance giants—at least when it comes to revenue.

In 2015, Berkshire Hathaway still managed to post an 8.3% increase in revenue to $210.8 billion, keeping its fourth place on the Fortune 500. And even though Exxon Mobil’s revenue cratered 35.6% to $246.2 billion, it was still able to hang on to second place on the list. Meanwhile, Facebook’s revenue rose 43.8% to $17.9 billion last year, skyrocketing through 85 positions to take 157 on the Fortune 500.

Amazon on the other hand rose 11 positions to number 18 on the Fortune 500 after the e-commerce giant’s revenue rose 20.2% to $107 billion.