Thanks. Any idea by what % spam has reduced due to this?

% spam has probably increased by this, as it is only a barrier to entry to mass-mailers that aren't spammers. Examples are: Paypal, EBay, airlines (although a lot of airline email looks like SPAM to me). You have to verify your identity with state-issued documents for some (all?) of those programs. There are a lot of restrictions (contractual and technical) applied to the messages that are sent through such programs. They are too expensive and risky for spammers to make money using them; in fact, they are too expensive for almost anybody to bother signing up for them.