Take a mature industry - what are the sources of potential upside?
Growth, more customers, perhaps from new geographies/product categories
Efficiency improvements and thence profitability
Occasionally new product innovation.
Being a mature industry though, the chance of a break out innovation, that changes the face of the industry, is low. So your growth path for the industry tends to be tied to GDP growth in the end.
With tech though, you can have a revolutionary product, which doesn't do it by redistributing power, but by increasing the share of the pie for everyone.
And while doing this, tech still keeps the possibility of growth through diversification/geographical expansion AND efficiency improvements which will be discovered over time.
Sorry I am a bit tired, so I may not have made the most educational of responses.
Tech has moats. Tech is probably the least regulated global industry -- in absurd countries like India, tech companies thrive in spite of bureaucracy. In highly unstable places like Israel, tech companies can compete too. I suspect Africa will have tech as a #3 segment (after extractive mining and some kinds of (relatively destructive) agriculture).
Aviation is kind of the diametric opposite of this -- heavily regulated, capital intensive, and exposed to commodities and union labor.
I don't invest exclusively in tech, but I understand tech better than most other sectors, so I feel more comfortable with individual stock picking. I do index funds in most other segments (with the exception of oil, which I also understand, and transport/logistics). I do index funds for S&P 500, international, MCSI 3000, and specific other sectors.
What is the best tool for testing things like this (are there big datasets available for public stock markets?)
From everything I've seen, beta for tech stocks has been positive for basically all of the past 40 years, and S&P has been up by a lot, so yes, tech stocks did well. That doesn't really say it did better than other sectors individually, but better than average.
Trains also had huge amounts of skull duggery going on, at a time where pump and dump scams involved people physically forging fake shares and selling them on the market to destroy the price of said stock.
Plus railways are cap intensive as well - tech investment comparatively is far lower, with a greater pay off.
If you think there is no monkey business in tech... well, I've got a bridge you can invest in:-)
I think that tech is certainly a growth sector, but does that translate into buying into stocks in the whole sector and coming out ahead? There is some pretty vicious competition, no? DEC, SGI, Yahoo, Altavista, Wang Laboratories, Commodore International... the list of companies that once flew high and then tanked is fairly long.
For a retirement fund, I still think tech gives the best 50 year returns, as a sector.