What do investors bidding up tech shares know that the rest of us don’t?

The biggest story to come out of the post-March stock market boom has been explosive growth in the value of technology shares. Software companies in particular have seen their fortunes recover; since March lows, public software companies’ valuations have more than doubled, according to one basket of SaaS and cloud stocks compiled by a Silicon Valley venture capital firm.

Such gains are good news for startups of all sizes. For later-stage upstarts, software share appreciation helps provide a welcoming public market for exits. And, strong public valuations can help guide private dollars into related startups, keeping the capital flowing.

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For software-focused startup companies, especially those pursuing recurring revenue models like SaaS, it’s a surprisingly good time to be alive.

Indeed, after COVID-19 hit the United States, layoffs and rising software sales churn were key, worrying indicators coming out of startup-land. Since then, the data has turned around.

As TechCrunch reported in June, startup layoffs have declined and software churn has recovered to the point that business and enterprise-focused SaaS companies are on the bounce.

But instead of merely recovering to near pre-COVID levels, software stocks have continued to rise. Indeed, the Bessemer Cloud Index (EMCLOUD), which tracks SaaS firms, has set an array of all-time highs in recent weeks.

There’s some logic to the rally. After speaking to venture capitalists over the past few weeks, notes from EQT Ventures‘ Alastair Mitchell, Sapphire’s Jai Das, and Shomik Ghosh from Boldstart Ventures paint the picture of a possibly accelerating digital transformation for some software companies, nudged forward by COVID-19 and its related impacts.

The result of the trend may be that the total addressable market (TAM) for software itself is larger than previously anticipated. Larger TAM could mean bigger future sales for and more substantial future cash flows for some software companies. This argument helps explain part of the market’s present-day enthusiasm for public tech equities, and especially the shares of software companies.

We won’t be able explain every point that Nasdaq has gained. But the TAM argument is worth understanding if we want to grok a good portion of the optimism that is helping drive tech valuations, both private and public.