Your impression of Smalltalk is quite incorrect. Smalltalk is used for all kinds of applications, both big and small, including major commercial enterprise applications. Cincom, Instantiations, and GemTalk are the three major commercial Smalltalk vendors and they have enterprise customers from around the world (examples: Cincom customers, GemTalk customers). Open source Pharo also has many users around the globe: Pharo users. Check out ALLSTOCKER.
I wrote a story about Hong Kong-based OOCL (Orient Overseas Container Lines) and their huge online tracking system: Who uses Smalltalk?
In the early 1990’s, Smalltalk almost became the enterprise standard programming language when IBM chose it as the centrepiece of their VisualAge enterprise initiative to replace COBOL. (Unfortunately, that role was eventually usurped by Java.) Of course, enterprise COBOL applications can be very, very big.
In the early 2000’s, the U.S. joint military wrote a million-line battle simulation program called JWARS using Smalltalk. This program outperformed a similar simulation called STORM, written by the U.S. Air Force using C++.
Anecdotally, then, there are plenty of evidence to show how productive Smalltalk is, because the number one reason companies use Smalltalk is for its productivity and impressively short “time to market.” Many companies use Smalltalk essentially as a “secret weapon” against their competitors. This is corroborated by many veteran Smalltalkers I’ve spoken to (at Cherniak Software and Simberon, for example, both major Smalltalk houses, and at Instantiations). Even outside of the Smalltalk community, the language has a well-known reputation for productivity. I’ve heard this over a great many years (I’ve been in IT for over 30 years).
There are only two kinds of evidence: statistical and anecdotal. Take your pick. I’ve presented both.