Mcap** to Transaction Value Ratio (MTV Ratio) is similar to the PE Ratio used for stocks.
When Bitcoin's MTV is high, it indicates that its Mcap valuation is outstripping the value being transmitted on its payment network, this can happen when the network is in high growth and investors are valuing it as a high return investment, or alternatively when the price is in an unsustainable bubble.
Bitcoin's MTV is calculated by USD Mcap by the USD volume transmitted through the blockchain. The USD value transmitted is an estimation by Blockchain.info
**Mcap is Bitcoin's Money Supply expressed in USD value (we use the term Mcap to distinguish it from Market Capitalisation used in stockmarkets)