One important indicator suggests that global equities are in a bubble.
I’m thinking of the ratio of the money stock to share prices in developed economies. Common sense says this should matter. If investors own lots of cash relative to equities, it’s a sign that the latter are cheap and that any rebalancing of portfolios is more likely to be from cash into shares than vice versa, which would drive prices up. By the same token, if the ratio of equities to cash is high it is a sign that shares are over-owned and so markets are in danger of falling.