**Table 1. Key differences between the current and previous simulations**

||**Current Global Simulations**|**Previous Global Simulations**|
|---|---|---|
|Expected learning gain or<br>school productivity (in HLO<br>points / year) in a regular<br>schoolyear|Varies by countries’ income level. Sa|me as inAzevedo, Hasan et al. 2021.|
|Mitigation effectiveness|Varies by scenario, and by country’s income level.<br>Optimistic scenario: 10% for low-income, 14% for<br>lower-middle-income, 20% for upper-middle-income,<br>and 30% for high-income countries.<br>Intermediate and pessimistic scenarios: 5% for low-<br>income, 7% for lower-middle-income, 10% for upper-<br>middle-income, and 15% for high-income countries.|Varies by scenario, and by country’s income level. See<br>Azevedo, Hasan et al. 2021.<br>Optimistic scenario: 20% for low-income, 28% for<br>lower-middle-income, 40% for upper-middle-income,<br>and 60% for high-income countries.<br>Intermediate scenario: 10% for low-income, 14% for<br>lower-middle-income, 20% for upper-middle-income,<br>and 30% for high-income countries.<br>Pessimistic and very pessimistic scenarios: 5% for low-<br>income, 7% for lower-middle-income, 10% for upper-<br>middle-income, and 15% for high-income countries.|
|Baseline Values|Global Learning Poverty Database from June 2022<br>(different from what was used inAzevedo 2020).<br>Includes recent results for PASEC 2019, TIMSS 2019,<br>LLECE 2019, and from new assessments, such as SEA-<br>PLM 2019 and AMPL-b 2021 (Zambia), as well as NLA<br>from Lesotho that has undergone policy linking. This<br>applies only to Learning Poverty simulations.<br>Global HCI database from 2021 (used inAzevedo,<br>Hasan et al. 2021).|Global Learning Poverty Database from October 2019<br>(used inAzevedo 2020).<br>Global HCI database from 2021 (used inAzevedo,<br>Hasan et al. 2021).|
|Learning Poverty reporting<br>window|The new Learning Poverty window for aggregate<br>estimates is ±4 assessment years around 2019. There are<br>some exceptions: Afghanistan, Kyrgyzstan, Lesotho,<br>Pakistan, Tunisia, Uganda, and Yemen. Population<br>estimates for 2019 are used for aggregate calculations.|The previous Learning Poverty window for aggregate<br>estimates was ±4 assessment years around 2015.<br>Population estimates for 2015 were used for aggregate<br>calculations.|
|Data on actual school closures|UNESCO school closures tracker for February 2020 –<br>February2022.|Not available at the time. The length of school closures<br>was scenario-based.|
|Length of period in school<br>years|2, minus country-specific breaks.|1.|
|Share of the school system<br>closed|Schools can be considered partially closed.|Education system was assumed to be fully open or fully<br>closed.|
|Country-specific school<br>closure information|Yes. UNESCO school closure tracker has country-<br>specific information.<sup>15</sup>|No. All countries were assumed to have the same length<br>of school closures, depending on the simulation<br>scenario.|
|School closure assumptions:<br>Optimistic|Observed country-level school closures, partial closures<br>are assumed to affect 75% of the student population.|Schools assumed to be closed uniformly for 3 months<br>in a 10-month school year.|
|School closure assumptions:<br>Intermediate|Observed country-level school closures, partial closures<br>are assumed to affect 85% of the student population.|Schools assumed to be closed uniformly for 5 months<br>in a 10-month school year.|
|School closure assumptions:<br>Pessimistic|Observed country-level school closures, partial closures<br>are treated as full closures.|Schools assumed to be closed uniformly for 7 months<br>in a 10-month schoolyear.|
|School closure assumptions:<br>Very Pessimistic|N/A|Schools assumed to be closed uniformly for 9 months<br>in a 10-month school year.|

> 15 We impute missing values for share of school system closed by using the regional average by income level for countries with learning data (LAYS, LP, or PISA). The countries are: Belarus; Burundi; the Democratic Republic of Congo; the Republic of Congo; the Arab Republic of Egypt; Hong Kong SAR, China; the Islamic Republic of Iran; the Republic of Korea; Kosovo; Macao SAR, China; Micronesia, Fed Sts.; Nauru; St Kitts and Nevis; St Lucia; St Vincent and the Grenadines; Tajikistan; and the Repbulci of Yemen.

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