The gambling or culture adviser will show you how many tourists visited your city today and yesterday. If you mouse over the number of tourists, you see a tooltip with a breakdown by wealth level
2,000 / 10,000 low wealth
3,000 / 12,000 medium wealth
80 / 80 high wealth
What does the number in the denominator mean? The numerator appears to be the number of tourists of that wealth level who visited the city.