Insantiate Loop Issue

Hi. I've written a script that checks the number of Villagers against a Population int. If the Villager < Pop then it Instantiates a prefab of a Villager until they = Pop. The script works, but on run time it throws out an "Assertion failed" error. Code below;

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class Population : MonoBehaviour
 {
 
     public int Pop;
     public int PopGrowth;
     public Text PopText;
     public Text PopGrowthText;
 
     //Variables for spawning population
     public GameObject Villager;
     public GameObject[] Villagers;
     public GameObject TownHallSpawn;
 
     public int[] popArray;
 
 
     void Start()
     {
         Pop = 10;
         PopGrowth = 1;
         StartCoroutine(StatUpdate());
 
     }
 
     IEnumerator StatUpdate()
     {
         
 
         Villagers = GameObject.FindGameObjectsWithTag("Villager");
 
         int VillagerTotal = Villagers.Length;
 
         if (VillagerTotal == Pop)
         {
            yield break;
         }
 
         else if (VillagerTotal < Pop)
         {
             while (VillagerTotal < Pop)
             {
                 Instantiate(Villager, new Vector3(Random.Range(-2.0f, 2.0f), 0, Random.Range(-2.0f, 2.0f)), transform.rotation);
                 VillagerTotal++;
                 yield return new WaitForEndOfFrame();
             }
         }
         else
         {            
             Pop = Pop + PopGrowth;
             Instantiate(Villager, new Vector3(Random.Range(-2.0f, 2.0f), 0, Random.Range(-2.0f, 2.0f)), transform.rotation);
             yield return new WaitForSeconds(60);
         }
         StartCoroutine(StatUpdate());
     }
 
     void Update()
     {
         UpdatePop();
 
     }
 
     void UpdatePop()
     {
 
         PopText.text = "Pop: " + (int)Pop;
         if (PopGrowth >= 0)
         {
             PopGrowthText.text = "+" + PopGrowth;
         }
         else if (PopGrowth < 0)
         {
             PopGrowthText.text =  "" + PopGrowth;
         }
         
     }
 }

Is this an issue with the code or Unity? Most likely the code ;)