One is that no matter how sophisticated the portfolio analysis used, itis simply notpossible to discount mathematically the chances that Damien Hirst's polka dots are going to appeal more in 20 years than Jeff Koons's dinner plates.
Meanwhile, since the market does not know by how much the government will allow Petrobras to raise gasoline prices, itisnot yet possible to calculate the net impact on inflation.
While itisnot yet possible to determine how large such profits will actually be -- the terms of some of the transactions now under negotiation with the USSR make the accounting procedures applied to leveraged buyouts look simple -- in terms of the overall national trade picture, they are likely to remain a drop in the bucket.
Itisnotpossible to tell from the published results how many of those who actually sat Highers achieved them - and the attainment "percentages" can also be more than 100.
As I have written previously, itisnotpossible to reform taxes unless the reformers first agree on how much the new revenue code is supposed to collect.
Because many of us are adding new contributions to our accounts or withdrawing funds from our accounts each year itisnotpossible to equate the published annual return to your own holdings and know how you did.