We really don't know very much, certainly not enough to plan

This point has of course been made before, even by the occasional person even more illustrious than we are. However, it does bear repeating, we just don't know very much about our world:

The Current Population Survey Annual Social and Economic Supplement (CPS ASEC) is the source of the nation’s official household income and poverty statistics. In 2012, the CPS ASEC showed that median household income was $33,800 for householders aged 65 and over and the poverty rate was 9.1 percent for persons aged 65 and over. When we instead use an extensive array of administrative income records linked to the same CPS ASEC sample, we find that median household income was $44,400 (30 percent higher) and the poverty rate was just 6.9 percent. We demonstrate that large differences between survey and administrative record estimates are present within most demographic subgroups and are not easily explained by survey design features or processes such as imputation. Further, we show that the discrepancy is mainly attributable to underreporting of retirement income from defined benefit pensions and retirement account withdrawals.

Note that this is the US Census analysing their own numbers. And note how far out they are, an entire 30% of median income. On the basis that, you know, people lie about their income.

All of which is an excellent example of what Hayek was pointing out, we don't in fact have the information to be ab le to plan the economy in any meaningful manner. Here, what value all those plans to reduce elderly poverty when we're 30% out in our estimation of how much elderly poverty there actually is? And that's from the best figures available to government.

Our ability to change things is severely limited by our inability to know how things actually are.