According to Grand View Research, the global artificial intelligence (AI) market was worth an estimated $62 billion in 2020 but could grow 40% annually through 2028. If you don't yet have AI stocks in your long-term portfolio, it might be time to start thinking about it. The market's recent sell-off of technology and high-growth companies has created a great buying opportunity for bold and patient investors. Here are three top AI stocks building moats around their algorithms and whose stocks are attractively priced today. Technology can change at a blistering pace, and nobody can know for sure that the winners of today will still hold their crown tomorrow, a year from now, or a decade from now.

The first quarter delivered home-sale profits that were more than twice as high as anticipated, the company said. Zillow expected to make money primarily from transaction fees and from services such as title insurance--not from making a killing on the flip. The company's algorithm, which was supposed to predict housing prices, didn't seem to understand the market. Zillow was also behind on its target for home purchases. By the summer, it had the opposite problem, the company later acknowledged.

The automated valuable model is a machine learning model that estimates the value of a property, usually by comparing that property in question to …

In the last two months Michael Marks has turned down a dozen offers to make keynote speeches at conferences. His company, construction startup Katerra, is three years old, but the attention surge is very recent. "Construction technology has gotten kinda buzzy," he says. But more likely, interest in Katerra has spiked because in January, the company landed an astounding $867 million in venture funding led by the SoftBank Vision Fund. A deal of that size, led by the venture industry's most talked-about fund, will put a company on the map overnight.

Welcome to the world of AI. Last March, the online asset manager AlphaFlow launched its first so-called automated investment fund for real estate loans. Rather than tapping employees to search for investment opportunities, the company uses a computer program to sift through listings services and find mortgages to purchase based on property characteristics, borrower history, recent market data and other criteria. "We're not ready to take our hands off [our work]," said Ray Sturm, co-founder of the California-based company, explaining that humans still make the ultimate investment decision. But, he noted, machine-driven algorithms are doing increasingly more.

Now that every buyer and seller is accustomed to using an app to search for property information and the nearest coffee shop, tech companies are upping the ante on what an app or an online platform can do. Instead of just using technology as a supplement to a real estate transaction, several companies allow sellers to connect directly to buyers through an app or an online trading platform. Home builder Lennar Corp. has completed a year-long pilot program with Opendoor in Las Vegas to encourage buyers of Lennar homes to sell their properties to Opendoor and trade up to a newly built Lennar home. Sellers fill out an online form and Opendoor provides them with an offer within 48 hours. The homeowners can accept or decline the offer.