On Walmart's cash flow statement here:
The 'Cash, Equivalents, Start of Period' for 2018 is the same as the 'Cash, Equivalents, End of Period' for 2017 (6,867.0). (Please be aware, years are going from left to right, and are "Values in Millions Except for per-share items").
Why then is this not the same for 2018 and 2019, where it is 6,756.0 at EOP, and 7,014.0 at SOP. For 2019>2020, it is once again the same: 7,756.0! (Column dates Left to Right are 2017 2018 2019, 2020).
The amount of the previous year is a statistical value to determine the management's performance without impacts out of there responsibility. This impacts are the same impacts that cause the deviations you see in the financial statistic there. Two examples are:
Exchange rates: Global companies operate all around the globe, so a big share of their assets is valued in local currency (e.g. EUR) first and then converted in group currency (e.g. USD) for the group's balance sheet. The amount of End of Period 1 is converted with an exchange rate used for Period 1's balance sheet.
The amount of Start of Period 2 should be the same in the local currency, but might be different in group currency as the exchange rate could've changed.
tl; dr: End of Period 1 amount is impacted by different exchange rates than Start of Period 2 for all assets in non-group currency.
Different valuation of assets: It may be that between Period 1 and Period 2 the legal requirement for the valuation of assets changed. To keep the statistic of cash-flow development meaningful and present the true changes during the period, the amount at the beginning of period 2 is the amount at the end of period 1 but modified by the impacts of legal requirement changes for the 2nd period's accounting principles.
