google packages-are the refferals sponsorship is going down.........learn more

When Google introduced Google Pack referrals, AdSense publishers were paid up to $2 per successful conversion.
The payment scheme was revised this year and the Google Pack referral payout was reduced from $2 to $1 - the amount would vary depending on the geographic location of your visitors who install Google Pack.
I was looking at the the average payout rate (Earnings/Number of Conversions) for Google Pack in my AdSense account and as expected, there was a dip in February.

But a surprising part is that this dip got steeper as we moved into the month of March and all the more in April. Maybe Google is re-evaluating the payout rates for Google Pack Referrals? Or it’s just a temporary phase. What are your thoughts / experiences ?