due to government containment measures (“lock-downs”). Over time, adjustments are also made to the type of goods and services selected to reflect changes in the sorts of goods and services purchased by 'typical consumers'. New products may be introduced, older products disappear, the quality of existing products may change, and consumer preferences can shift. Both the sorts of goods and services which are included in the "basket" and the weighted price used in inflation measures will be changed over time to keep pace with the changing marketplace. Different segments of the population may naturally consume different "baskets" of goods and services and may even experience different inflation rates. It is argued that companies have put more innovation into bringing down prices for wealthy families than for poor families. Inflation numbers are often seasonally adjusted to differentiate expected cyclical cost shifts. For example, home heating costs are expected to rise in colder months, and seasonal adjustments are often used when measuring for inflation to compensate for cyclical spikes in energy or fuel demand. Inflation numbers may be averaged or otherwise subjected to statistical techniques to remove statistical noise and volatility of individual prices. When looking at inflation, economic institutions may focus only on certain kinds of prices, or special indices, such as the core inflation index which is used by central banks to formulate monetary policy. Most inflation indices are calculated from weighted averages of selected price changes. This necessarily introduces distortion, and can lead to legitimate disputes about what the true inflation rate is. This problem can be overcome by including all available price changes in the calculation, and then choosing the median value. In some other cases, governments may intentionally report false inflation rates; for instance, during the presidency of Cristina Kirchner (2007–2015) the government of Argentina was criticised for manipulating economic data, such as inflation and GDP figures, for political gain and to reduce payments on its inflation-indexed debt. Inflation expectations Inflation expectations or expected inflation is the rate of inflation that is anticipated for some time in the foreseeable future. There are two major approaches to modeling the formation of inflation expectations. Adaptive expectations models them as a weighted average of what was expected one period earlier and the actual rate of inflation that most recently occurred. Rational expectations models them as unbiased, in the sense that the expected inflation rate is not systematically above or systematically