Info: Are Nigerians changing their tack?

I've noticed a downward shift in the number of 419 scams arriving. My 419 archives show fifty-something 419 scams per month in the months of June, July, and August, but then a 50% drop in September, and projections for the remainder of October are looking similarly low. At the same time, I noticed that a recent job scam had a very Nigerian feel to it (despite pretending to come from China). On investigation, I note that the modus operandi is very typical of the Nigerians (using a webmail system), and the sending system reports that the originating IP address was 80.88.141.71, which is allocated to Nigeria (delegated from "Emperion", Denmark, to Nnamdi Nwokoro of Benin City, Edo state, Nigeria, according to WHOIS data).

Perhaps the Nigerians have discovered that it's more profitable for them to engage in job scams rather than advance fee fraud? Unlike the Russians and other Eastern Europeans (who tend to run job scams in conjunction with phishing), I get the impression that the Nigerians prefer forgery, and target the USA. According to an article at Snopes, there is a lot of fraud involving forged cheques and money orders: individuals are persuaded to accept these and wire back 90% of the face value via Western Union (or some similar arrangement). Due to banking regulations in the US, the proceeds of the cheque become available before the cheque is fully verified. The recipient gets a rude shock later when the bank denies the cheque and reverses the deposit.