If you look at historic rates of return, four percent would be considered high. Pardoning the last 200 years, growth tended to be incremental. If inflation isn't high, that isn't a horrible return rate.
(While we're discussing predictions, I'm calling it now: Tesla to zero within ten years.)
I thought historic rate with Dividends is 8-10%? He's saying 4% with Dividends.
Bogle said, "Stocks will return about 4% a year for the next decade or so rather than the 10% average annual returns of recent decades."
Compound growth is a modern phenomenon that economists still struggle to explain. Historically, growth tended to be incremental. Imagine the standard of living stretching from 2000 BC to 1500 AD. Ignoring regional anomalies (ex. Rome annexing its neighbours and stealing their wealth, Mehmed II's expansion in the Balkans and Asia minor), there wasn't much economic growth to speak of. Even if you extend that a few thousand years back or hundred years forward, you still won't see much growth.
One hundred years ago, cowboys were shooting injuns in the Wild West. Now west coast hipsters are sitting at a Starbucks on that land with a gorgeous Dell XPS 15, with coffee from Africa, and an iPhone from China that can connect them to billions of people on services created by companies that are now the largest companies in the world despite being less than ten years old. (It's not even regionally isolated; growth like this is occurring in hundreds of countries.) Never before in the world has growth like that been considered the norm.
(Stocks and the growth of the economy aren't directly related. For example, if you have a set of companies taking a progressively bigger slice of the pie, the pie can be shrinking but the companies' stocks be growing.)