DI rolls "heading for collapse" in US?

The NCPA has a piece on the soaring disability insurance numbers in the US:

Since 1970, the number of individuals receiving DI has grown sixfold (from 1.4 million to 8.8 million), and the program expenses have grown tenfold, which is unsustainable.

How does NZ compare?

Using sickness and invalid benefit annual totals, the numbers have grown from 14,310 in 1970 to 147,029 in 2011 - more than ten-fold. Measured against the total population there are 28 claimants per 1,000 in the US compared to 33 per 1,000 here.

(That ignores long-term ACC claimants.)

Meanwhile both country's populations have grown by around 55 percent over the same period.

Still, neither country's problem is as big as some EU countries.