First of all, given the global economic slow down of the last decade and continuing into this one, the universal USD 1.25 PPP metric to ascertain who is living below or above the poverty line needs to be adjusted upward to reflect the reality in most countries, whether in the West or South. Next, most of us know that a lot of countries manipulate data (even where it is easily available) for all sorts of reasons. So, for us to have reliable and meaningful information, we need to address the root causes of why those that are this charged with crucial responsibility choose to mislead the general public. In addition to your discussion above, poor countries sometimes lack data availability due to the informal nature of many of the activities that would be used as source data or adequate training and awareness to collect whatever data is available on a timely basis. With the increase in technology, media, globalization, etc many people in poor countries have developed a distrust of those they perceive as being in power (politicians, donors, the elite) such that when they are approached for anything, especially information, they are not forthcoming or in some cases you will be outright attacked since they conclude that you want to sell this information for personal gain. So educating the public as to why this excise is for their benefit prior to carrying it out is very important.