What was actual voter turnout in El Salvador?

El Salvador's Supreme Electoral Tribunal reported that voter turnout for the February 3 presidential election was quite low.   The TSE reported that only 51.9% of eligible voters turned out to vote.   This is the number which is being widely reported and which is being viewed as a level of voter disenchantment with politics in El Salvador.   But I don't think that number is accurate and the actual turnout is better.

The TSE calculates voter turnout by using the number of eligible voters on the election registry -- 5,268,411 and the number of votes cast on February 3 -- 2,733,178.  Of that number of 5,262,463 are citizens which the TSE believes live in the country of El Salvador, while the remainder were the 5948 Salvadorans living abroad who managed to get on the mailing list for an absentee ballot. 

But I believe the number of voters on the registry is significantly overstated.    

The best source for data on the current population of persons living in El Salvador comes from the 2017 Multiple Purpose Household Survey conducted by El Salvador's census ministry and released in May 2018.    That survey calculated the current population living in El Salvador as 6,581,860.    According to that survey, 2 million children and youth are under age 18, the legal voting age.  This would suggest that the actual quantity of eligible voters for the 2019 election was approximately 4,580,000 or almost 700,000 less than the number of people on the voter registry.

Using 4,580,000 rather than 5,268,411 eligible voters produces a voter turnout of 59.6%, considerably higher than the reported number.

What could explain the discrepancy?   My educated guess is that the TSE, and the ministry which maintains the registry of Documents of Unique Identity (DUIs) from which the electoral registry is created, have had challenges in maintaining that database.   In particular, people who have migrated from the country have not updated their addresses on their DUIs and so remain listed as citizens residing in the country.  In addition, people who have died have not been removed from the database.  As a consequence, the number of persons on the election rolls is overstated compared to the number of eligible votes who actually are alive and living within El Salvador.

This is a problem which the TSE should attempt to address before the next elections, along with addressing the problems surrounding voting in elections from outside of the country.