As the spring house-hunting season approaches, tight inventory and rising prices are casting a lengthening shadow over the plans of starter homebuyer across the United States. And guess where the crisis is most pronounced?

Oakland.

That’s right. According to a new Trulia report on the 100 largest U.S. metro areas, Oakland is as bad as it gets when it comes to buying a starter home. The rest of the top five, in order, are Los Angeles, San Jose, San Francisco and Sacramento.

Compared to the rest of the nation, the Bay Area is “taking the biggest hit,” said Ralph McLaughlin, chief economist for Trulia, which released the quarterly price report titled, “House Arrest: How Low Inventory is Slowing Home Buying.”

Of the top 10 U.S. metro markets showing the sharpest decrease in starter home affordability since 2012, nine are in California. The report defines a starter home as one that’s priced in the bottom third of all homes in the market — where first-time buyers often look. Similarly, Trulia defines starter homebuyer as those whose household incomes fall in the lower third of the income distribution for a given metro area. In the Oakland metro area, that means an income of $52,700 and under; in San Jose, of $64,900 and under; in San Francisco, $62,000 and under.

Here are three snapshots of what’s happening in our own region:

In the Oakland area — where the tech boom has spread, driving up prices — the typical buyer of a starter home would have to spend 69 percent of household income to afford a 30-year fixed mortgage, with 20 percent down. That’s 29 percent more of the income than would have been needed in 2012. The median price of a starter home in the Oakland area is $374,000, according to the report.

As bad as that sounds, consider the plight of San Jose starter homebuyer, who would have to spend 87 percent of household income to afford a mortgage — 27 percent more than in 2012. The median price in the San Jose metro area is about $586,000.

Finally, San Francisco metro buyers would have to pay a whopping 110 percent of household income to afford a starter home mortgage — 25 percent more than in 2012. The median San Francisco metro price is $714,000. “I’m proud to be from the Bay Area and to see how much economic activity is here and how much technological advancement,” said McLaughlin, who grew up in San Jose’s Berryessa district and moved two years ago from San Francisco to Oakland. “At the same time, I’m ashamed by how those in the middle and lower income brackets are essentially becoming locked out of the housing market.” Given the demand in pricey markets like the Bay Area, a new phenomenon is growing: When it comes time to move, middle-tier homeowners “increasingly find themselves looking down the housing ladder” toward houses priced in the lower third of the market, McLaughlin said. Here’s an example: Say a worker who owns a comfortable place in more affordable Contra Costa County suddenly must move close to a new job in San Jose. He or she may wind up downsizing because of the increased cost of housing. “Or someone who is moving into the Bay Area from another market — even from Sacramento,” McLaughlin said. “Normally they might want to buy a four-bed, three-bath house for the family. But they get there and they can’t afford it.” Again, they downsize, sometimes dramatically. As those middle-tier buyers move down the housing ladder, it exerts pressure on prices in the bottom third of the market, intensifying the competition for first-time buyers. Trulia reports that of the 100 largest metro areas in the U.S., 95 have shown a decrease in the number of starter homes since 2012. Of the 10 metro areas showing the biggest decline, all are in the West and South. Salt Lake City tops the list: In four years, the number of starter homes there has plummeted from 1,243 to 151. That’s an 88 percent drop-off. The report cites three reasons for falling inventory in the starter home and mid-tier “trade-up” categories:

Investors snapped up foreclosed homes during the recession and converted them to rentals.

A larger share of lower-priced homes remains underwater compared to higher-tier homes. Their owners therefore are less likely to sell and take a loss.