Where is America’s tech and software industry thriving? In a new study conducted for the San Diego Regional Economic Development Corp., researchers took an interesting stab at that question, assessing which metro areas have the strongest concentrations of software developers, spread across a broad array of industries, as well as the best compensation and job growth, and access to venture capital funding.

What they found is a geography dominated by traditional tech centers, particularly those with strong universities. The San Jose, Calif., metro area and Seattle led the way, followed by San Francisco and Boston. The back half of the top 10 is a bit more surprising, featuring Baltimore, Atlanta and Washington, D.C.

All these metro areas have outsized concentrations of software developers compared to the national average. San Jose boasts an unparalleled concentration of talent, with 69.7 software developers per 1,000 employees, five times the average among the nation’s 50 largest metro areas. Seattle runs second with a concentration of 38.3 per 1,000 workers.

These areas tend to have different areas of expertise. Software is now critical to many industries; not just computers, but also manufacturing, finance and services. In places like Washington and Baltimore, much of the work is related to the federal government, as is also true for seventh-ranked San Diego, which has long had a major military presence. The Bay Area, of course, dominates fields such as new media, search and computer systems design. In San Diego they tend to work in scientific research much more than their counterparts elsewhere in California.

These ratings matter not so much in terms of the number of jobs — software publishers have added a net of 50,000 jobs since 2001, up 19%. Yet as software use has grown, there has been impressive growth across the board in the number of programmers: According to EMSI, the profession has added 350,000 jobs since 2003, 27 percent growth. Jobs in this category also carry a decent paycheck, with a median hourly wage of $44. In 2015, notes the San Diego report, software firms received $23.8 billion in venture capital—a 400% increase in investment since 2010.

Greater Concentration Or Decentralization?

Clearly metro areas like San Diego have good reason to sell themselves as software hotspots; the industry has grown three times faster in employment than the overall economy and expects 18.1 percent growth this year.

But not all hotspots are equal, which is also true of tech in general. Indeed, according to EMSI data, the share of high-tech employment in the Silicon Valley/San Jose area’s economy  is more than six times the national average. Others that rank more than twice the national average include Washington D.C., San Francisco, Seattle, Boston, Raleigh and Austin, who are also our leaders in software. Others on the software list, such as San Diego, are above the national average, but only slightly – San Diego’s overall share of tech jobs relative to the national average has actually declined since 2001.

Clearly metro areas that have had long-established tech communities do well, but perhaps this may prove not so much the wave of the future but the resonance of the past. In fact, if we look at which areas are having the most tech growth, many are not what would be widely considered tech hubs. Indianapolis, for example, has seen a 102 percent growth since 2001 in tech jobs while Las Vegas, Jacksonville and Nashville have seen strong growth of over 80 percent or more, and each has boosted its share of jobs in tech dramatically.

But perhaps the most critical advantage is to those areas which have both high concentrations of tech jobs and also rapid growth. These areas would seem best positioned to advance in the coming years and include some of the study’s software superstars. Austin for example has expanded tech employment since 2001 by 89% and boosted its location quotient (the ratio of local share to national share of jobs in a sector) for tech employment from 2.14 to 2.32. Raleigh, San Francisco and Seattle have also expanded both in relative and absolute tech employment.

Essentially we may be witnessing two parallel, and notionally conflicting developments, notes analyst Mark Schill of the Praxis Strategy Group. There are clearly a series of regions, as identified by the report, that have achieved critical mass in software and across many other tech fields. Yet at the same time, the most rapid growth is taking place largely in non-traditional tech hubs, including places like Salt Lake City, San Antonio, and Phoenix, all seeing rapid growth in tech jobs as well as a growing concentration.

Big City Tech Bust

The software study also reveals something that might not please many advocates for an urban-centered tech world. Despite their strident efforts to promote themselves as tech and software centers, our three largest cities — New York, Los Angeles and Chicago — have not fared terribly well. The one dense urban center that has seen rapid growth in terms of tech jobs and share has been the San Francisco-Oakland area, which has the advantage of being located next to Silicon Valley and the dominant centers of venture capital. The region also includes parts of the Peninsula, like San Mateo, that have emerged as important suburban tech hubs.

In Los Angeles, the decline of the aerospace industry has stripped away its primary tech anchor. L.A., Chicago and NYC have posted average tech growth. If all the hype ascribed to “Silicon Alley” or “Silicon Beach” were matched by their performance, the numbers would look very different.

This can be seen by comparing growth in software jobs, an area where dense urban areas are widely held to have big advantages. Between 2010 and 2014 software employment expanded only 13.6 percent in New York, and 11.7 percent in Los Angeles, compared to the median growth of 13.4 percent.

This parallels their less than spectacular performance in our analysis of EMSI tech employment. Despite the almost endless discussion of Gotham as tech job hub, New York’s tech growth since 2001 has been a below average 27% while its tech locational quotient has dropped from 1.15 to 1.06, roughly the national average. Chicago did even worse, growing just 24% and actually seeing its locational quotient drop to 0.98, below the national average. But the big loser has been Los Angeles, once a premier tech hub, but clearly losing its edge. Since 2001 L.A. has managed only 9 percent tech growth and its relative concentration in tech jobs has fallen to 0.74, well below the national average.

Looking Ahead

The San Diego study, as well as our own analysis, suggests a diverse future for software and other tech related fields. First, there are the clear winners — places like San Francisco, Silicon Valley, Raleigh, Seattle, Austin — which continue to add both new jobs and boost their share of tech and software employment. Areas like these enjoy both momentum and critical mass, which all but guarantees a prosperous future for these metro areas as software comes to dominate more of our lives, and other industries.

The second group, which includes key players like San Diego and Boston, will be fighting to hold onto their positions. They have experienced some growth, but their share of tech jobs has been falling and they may not have the momentum to make up for other disadvantages such as high housing prices and taxes. Such things may not slow superstar cities like San Francisco, but they seem to take some of the wind out of the sales of these less dynamic tech centers.

Third, and most troubling, will be those places like New York and Los Angeles where the tech economy is often hailed as a savior, but does not seem, in relative terms, to be living up to the feverish advertising. Here high housing prices may be exacting a strong toll on the workforce. NYC and L.A. are both among the bottom six in terms new jobs in STEM (science, technology, engineering and mathematics-related positions); both actually have lost such workers since 2001, and now have workforces considerably less skilled in tech fields than the national average.

Finally, and this is not something widely acknowledged, has been the strong gains of less expensive, less heralded cities. They do not always have above average concentrations of tech and software workers, but are experiencing impressive gains. Take Phoenix, where tech employment has expanded 78 percent since 2000, while software employment has grown 28.8 percent since 2010. Phoenix’s tech location index is, remarkably, now higher than that of Los Angeles. Other, not widely appreciated big gainers in software include Nashville (43.5 percent gain), Atlanta (48.6 percent) and Charlotte (up 42 percent).

Given the ability of software firms to locate where they wish due to the intrinsic nature of their industry, we should expect not just consolidation to continue in certain markets, but also a simultaneous rapid dispersion of tech jobs. Yet neither the agglomeration nor the dispersion is likely to be evenly distributed. Among the nation’s 53 largest metropolitan areas, just 20 saw their relative concentrations of high-tech employment increase since 2001. Mapping the future of tech and software employment will need to consider both factors and those regions which fit neither the low-cost model or that of the hyper-concentrated area may need to sit and reconsider how they can get back into the digital game.

This piece first appeared in Forbes.

Cross-posted at New Geography.