Total Domestic Market
The total domestic stock market invests in virtually every company in a home country, with the percentage of each company set by their market cap. So large companies take up a proportionally larger percentage of the index than small companies.
Note that while most people think of the stock market as “always going up”, it has suffered multiple rolling decades of compound losses. Selecting complementary assets to balance those down years can help smooth out the ride while delivering more consistent returns.