The Force That Compounds
In the short run economies wobble around their trend; in the long run the trend is everything. An economy growing 2% a year doubles living standards every ~35 years; at 7%, every decade. The rule of 70 does the arithmetic:
Compound growth is why small differences in rates dwarf every other economic question over a generation.
Where growth comes from:
- Physical capital: more machines and infrastructure per worker — but with diminishing returns: the tenth truck adds less than the first.
- Human capital: education, skills, and health embodied in workers.
- Technology: better recipes for combining the same inputs. Unlike capital accumulation, ideas don't run into diminishing returns — one blueprint serves everyone at once. This is the engine of sustained growth.
- Institutions: property rights, courts, stable money, honest administration. The invisible infrastructure that decides whether saving, studying, and inventing are worth anyone's while.
Why institutions come first: capital can be bought and technology copied, but no one invests where contracts don't hold. The clearest natural experiments — countries split by a border and an institutional regime — show the same people and geography diverging by an order of magnitude within decades.
Growth is not a windfall; it is what happens when a society makes accumulation and invention safe and rewarding, then lets compounding do the rest.
The three engines of growth
| Engine | What it adds | Diminishing returns? |
|---|---|---|
| Physical capital | More machines per worker | Yes — the tenth truck adds less |
| Human capital | Skills, education, health | Yes, eventually |
| Technology | Better recipes for the same inputs | No — one idea serves everyone |
Tip: Run the rule of 70 on any headline: 2% growth doubles living standards in ~35 years; 7% in ~10. Over a generation, nothing else in economics competes with a percentage point of growth.